Code
P1153
LEXUS
P — Powertrain
Air/Fuel Ratio Sensor Circuit Response Malfunction Bank 2 Sensor 1
Views:
UK: 21
EN: 37
RU: 19
AI status
Completed
Completed
100%
Causes
- Faulty air/fuel ratio (wideband/UEGO) sensor (Bank 2, Sensor 1)
- Open, shorted or corroded wiring or connector to the sensor
- Poor or missing sensor ground or power supply (heater circuit)
- Sensor contaminated by oil, coolant, fuel or deposits
- Exhaust leak upstream of the sensor
- Fuel delivery problem (low/high fuel pressure, injector issue) causing abnormal AFR
Symptoms
- Malfunction Indicator Lamp (MIL)/Check Engine Light illuminated
- Poor fuel economy or rich/lean running
- Rough idle or hesitation under acceleration
- Hard starting or extended warm-up enrichment
- Failed emissions test (high HC/NOx/CO or incorrect lambda)
What to check
- Retrieve trouble codes and freeze-frame data with a scan tool; record operating conditions when the code set
- Monitor live data: AFR (Bank 2 Sensor 1) waveform, heater status, and compare to Bank 1 Sensor 1
- Check short-term and long-term fuel trims for signs of rich/lean bias
- Visually inspect sensor, wiring harness and connector for damage, corrosion, or exhaust soot/oil
- Check for exhaust leaks upstream of the sensor
- Verify battery voltage and ground integrity at ECU and sensor harness
Signal parameters
- AFR/wideband sensor output should vary continuously with air–fuel ratio and respond quickly to induced rich/lean changes
- Typical sensor output expected to change across the usable voltage/current range specified by the manufacturer (refer to service manual for exact values)
- Heater circuit: supply voltage present with ignition ON and proper heater current when cold (refer to service manual for expected voltage and resistance)
- Response time: sensor output should change promptly (seconds) when inducing rich (introduce propane or snap throttle) or lean (vacuum leak) conditions
- Compare Bank 2 Sensor 1 waveform and values with Bank 1 Sensor 1 for consistency
Diagnostic algorithm
- Verify the code with a scan tool and note freeze-frame data (engine load, RPM, temp, voltage).
- Inspect the sensor and harness visually for damage, contamination, burns or connector corrosion; repair as needed.
- With key ON (engine off), backprobe the sensor connector: verify reference/power (heater supply), ground, and signal presence per service manual. Check for battery voltage at heater supply circuit.
- Measure heater resistance (if specified) and compare to OEM spec. Replace sensor if heater is open or out of spec.
- Start engine and monitor live AFR/wideband sensor output. Induce a rich condition (brief propane or snap throttle) and a lean condition (introduce small vacuum leak) while watching response. Slow or no change indicates sensor or wiring fault.
- Check continuity and resistance of wiring between sensor and ECU; wiggle harness while monitoring live data to identify intermittent faults.
- Inspect for and repair any exhaust leaks upstream of the sensor; re-test after repair.
- Check fuel pressure and injector function if AFR indicates persistent rich or lean conditions that could mask sensor response.
- If wiring, connectors, heater and vehicle systems check OK but sensor does not respond properly, replace the AFR sensor (Bank 2 Sensor 1) with OEM or equivalent and clear codes.
- After repairs or replacement, perform final verification: clear codes, test drive under conditions that previously set the code, and confirm sensor response and fuel trims are normal.
Likely causes
- Damaged wiring or connector (most common)
- Failed/worn air/fuel ratio sensor
- Contamination of sensor element (oil or coolant) interfering with response
- Heater circuit open or no supply voltage
- Exhaust leak between cylinder head and sensor
Fault status
Status
P1153 — Air/Fuel Ratio Sensor Circuit Response Malfunction (Bank 2 Sensor 1). The upstream wideband/AFR sensor on bank 2 is not producing the expected signal or response rate, or its heater/power circuit is abnormal. Verify sensor, wiring, power/ground, and related systems before replacing parts.
Repair difficulty: Medium
Diagnostic time: 1-2 hours
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