Code
P1133
ALFA ROMEO
P — Powertrain
Upstream oxygen sensor signal out of range | Oxygen sensor B1-S1 fault
Views:
UK: 2
EN: 5
RU: 4
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
P1133
BMW
P — Powertrain
O2 Sensor Heater Control Circuit Bank 2 Sensor 1
Views:
UK: 13
EN: 24
RU: 23
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
P1133
BUICK
P — Powertrain
HO2S Insufficient Switching
Views:
UK: 13
EN: 24
RU: 22
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
P1133
CADILLAC
P — Powertrain
HO2S Insufficient Switching
Views:
UK: 15
EN: 26
RU: 28
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
P1133
CHEVROLET
P — Powertrain
HO2S Insufficient Switching
Views:
UK: 14
EN: 26
RU: 23
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
P1133
CHRYSLER
P — Powertrain
HO2S Insufficient Switching
Views:
UK: 13
EN: 24
RU: 23
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
P1133
DAEWOO
P — Powertrain
AT FUEL SOLENOID MAL
Views:
UK: 1
EN: 4
RU: 3
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
P1133
DAIHATSU
P — Powertrain
Rear bump device abnormal
Views:
UK: 4
EN: 6
RU: 5
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
P1133
FIAT
P — Powertrain
Upstream oxygen sensor signal out of range | Oxygen sensor B1-S1 fault
Views:
UK: 3
EN: 5
RU: 4
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
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Code
P1133
FORD
P — Powertrain
Bank 1 Fuel Control Shifted Lean
Views:
UK: 14
EN: 24
RU: 21
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
P1133
Generic
P — Powertrain
HO2S Insufficient Switching Sensor 1
Views:
UK: 17
EN: 28
RU: 26
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
P1133
GM
P — Powertrain
HO2S Insufficient Switching
Views:
UK: 16
EN: 35
RU: 32
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
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Code
P1133
GMC
P — Powertrain
HO2S Insufficient Switching
Views:
UK: 18
EN: 29
RU: 28
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
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Code
P1133
GWM
P — Powertrain
- Sensor 1 HO2S
Views:
UK: 1
EN: 4
RU: 4
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
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Code
P1133
HUMMER
P — Powertrain
Heated Oxygen Sensor (HO2S) Insufficient Switching Bank 1 Sensor 1
Views:
UK: 7
EN: 10
RU: 13
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
P1133
LAND ROVER
P — Powertrain
fuel control of bank 1 with lean deviation
Views:
UK: 3
EN: 8
RU: 7
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
Workshop Manuals
Repair manuals for LAND ROVER
3
Land Rover Defender 300Tdi — Workshop Manual (1996 model year)
Workshop Manual199,00 UAH
Land Rover Defender Workshop Manual Supplement & Body Repair Manual (1999 & 2002 MY)
Workshop Manual199,00 UAH
Land Rover Range Rover — Electrical Library (LRL 0453ENG, 2002)
Workshop Manual199,00 UAH
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Code
P1133
LEXUS
P — Powertrain
Air/Fuel Ratio Sensor Circuit Response Malfunction Bank 1 Sensor 1
Views:
UK: 14
EN: 24
RU: 24
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
P1133
LINCOLN
P — Powertrain
Bank 1 Fuel Control Shifted Lean
Views:
UK: 15
EN: 28
RU: 29
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
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Code
P1133
MAZDA
P — Powertrain
Bank 1 Fuel Control Shifted Lean
Views:
UK: 15
EN: 26
RU: 28
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
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Code
P1133
MERCURY
P — Powertrain
Bank 1 Fuel Control Shifted Lean
Views:
UK: 16
EN: 30
RU: 29
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
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Code
P1133
OLDSMOBILE
P — Powertrain
HO2S Insufficient Switching
Views:
UK: 15
EN: 26
RU: 28
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
Your experience will help others
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Code
P1133
Other
P — Powertrain
HO2S Insufficient Switching Sensor 1
Views:
UK: 15
EN: 28
RU: 24
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
Workshop Manuals
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Land Rover Defender 300Tdi — Workshop Manual (1996 model year)
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Code
P1133
SAAB
P — Powertrain
O2S Circuit. Low Voltage. Sensor 1.
Views:
UK: 2
EN: 4
RU: 3
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
P1133
SATURN
P — Powertrain
HO2S Insufficient Switching
Views:
UK: 16
EN: 30
RU: 22
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
P1133
SCION
P — Powertrain
Air-fuel ratio sensor circuit response malfunction
Views:
UK: 1
EN: 5
RU: 3
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
P1133
TOYOTA
P — Powertrain
Air/Fuel Sensor Circuit Response Bank 1 Sensor 1
Views:
UK: 16
EN: 26
RU: 25
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
P1133
VOLKSWAGEN
P — Powertrain
Oxygen Sensor Heating Circuit Bank 1 + 2 Sensor 1 Electrical Malfunction
Views:
UK: 15
EN: 30
RU: 24
AI status
Completed
Completed
100%
Causes
- Failed or contaminated upstream O2 sensor (Bank 1, Sensor 1)
- Open, shorted or corroded O2 sensor wiring or connector
- Faulty O2 sensor heater circuit or blown fuse/relay
- Exhaust leak upstream of the sensor
- Fuel delivery problems (low/high fuel pressure, leaking injector)
- Intake vacuum leak or faulty MAF/MAP sensor causing abnormal mixture
Symptoms
- Check Engine MIL illuminated
- Poor fuel economy
- Rough idle or hesitation
- Black smoke or rich-running symptoms, or lean surging
- Failed emissions test
- Possible hard starting when cold (if heater circuit failed)
What to check
- Read and record freeze-frame and live data for O2 sensor voltage, heater status, and short-term/long-term fuel trims (STFT/LTFT)
- Visual inspection of sensor, wiring harness and connector for damage, corrosion, or exhaust soot
- Backprobe O2 sensor signal at connector while engine running; observe voltage behavior
- Measure O2 sensor heater circuit voltage at key ON/CRANK and RUN conditions
- Measure heater resistance with sensor removed (cold) per manufacturer spec
- Wiggle test wiring while monitoring sensor voltage for intermittent faults
Signal parameters
- Narrowband upstream O2 sensor expected voltage: approximately 0.1–0.9 V, switching rapidly between low (lean) and high (rich) when closed-loop
- Good upstream sensor should switch frequently (typical cycle ~1–2 Hz under steady conditions)
- Heater circuit: supply voltage present with key ON; heater resistance typically low (example ranges 5–20 Ω) — check service manual for exact value
- If sensor output is stuck near 0.1 V (low) or 0.9 V (high) or shows very slow/no switching, it indicates a problem
Diagnostic algorithm
- Retrieve freeze-frame and DTC data. Confirm P1133 and note conditions when code set (engine temp, load, RPM).
- Perform a thorough visual inspection of Bank 1 Sensor 1 wiring and connector for damage, corrosion, or disconnection. Repair any physical damage.
- With a scan tool, monitor B1S1 voltage in real time at idle and during gentle throttle changes. Expected: rapid switching ~0.1–0.9 V. If stuck or out of range, proceed.
- Check O2 sensor heater circuit: with key ON, verify reference voltage/power to heater and ground continuity. Measure heater resistance with sensor disconnected and compare to spec. Replace sensor if heater open or out of spec.
- If heater and wiring are good but signal is abnormal, backprobe sensor signal with engine running. If voltage is implausible (stuck high/low) check wiring continuity to PCM and for shorts to battery or ground.
- Inspect for exhaust leaks upstream of the sensor and repair if present. Exhaust leaks can cause false lean/rich readings.
- Check fuel system and induction: measure fuel pressure, inspect MAF/MAP and intake for vacuum leaks, and review STFT/LTFT. Correct underlying fuel or air issues that can drive sensor out-of-range.
- If wiring, heater, fuel/air supply and exhaust are good and sensor signal is still incorrect, replace the upstream O2 sensor (Bank 1 Sensor 1) and clear codes. Re-test to verify normal operation and no recurrence.
- If code returns after sensor replacement, perform PCM input/output tests and consider PCM reprogramming or replacement as a last step.
Likely causes
- Sensor wiring/connector damage or corrosion
- Defective O2 sensor (stuck high/low or very slow response)
- Heater element open or insufficient heater voltage
- Intake/exhaust leak causing abnormal readings
- Contaminated sensor from oil, coolant, or silicone exposure
Fault status
Status
Upstream O2 sensor (B1S1) signal out of range / O2 sensor circuit fault
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Was this AI description helpful?
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