Code
P0031
Generic
P — Powertrain
HO2S Heater Control Circuit Low Bank 1 Sensor 1
Views:
UK: 29
EN: 91
RU: 71
AI status
Completed
Completed
100%
Causes
- Blown fuse or relay for O2 sensor heater circuit
- Open or high-resistance wiring or connector (broken wire, corroded terminal)
- Short to ground in the heater control circuit
- Failed upstream (Bank 1 Sensor 1) oxygen sensor heater element
- Faulty ECM or driver transistor in ECM
- Incorrect or poor ground or battery supply to heater circuit
Symptoms
- Check Engine MIL/SES illuminated
- Longer than normal warm-up time and increased emissions until sensor reaches operating temperature
- Poor fuel economy or driveability during cold start
- Possible rich/lean fuel trim corrections while sensor cold
- No obvious engine misfire or performance loss once warmed (unless sensor entirely failed)
What to check
- Read and record freeze frame and live data (O2 sensor heater status, commanded heater state, fuel trims)
- Visual inspection of sensor connector and wiring for damage, corrosion or melted insulation
- Check fuse(s) and relays related to O2 sensor heaters
- Measure heater element resistance at sensor (with sensor disconnected) and compare to spec
- Backprobe connector with key on and heater commanded to ON to measure supply voltage and ground control
- Perform wiggle test on wiring while monitoring heater voltage/current or checking for intermittent faults
Signal parameters
- Heater supply voltage: battery voltage when commanded (approx. 11–14.5 V) — voltage significantly below battery when commanded can indicate low circuit
- Heater element resistance (ambient): typical range ~2–20 ohms (varies by sensor). Very high or infinite resistance = open heater
- Heater current when energized: roughly 0.5–2 A depending on sensor design (measured indirectly by voltage drop across known resistor or clamp meter)
- Expected ECU driver behavior: switches to ground (or supplies voltage) to energize heater — when commanded ON measured voltage at sensor connector should be near supply
- Trigger threshold: an open/high-resistance or measured voltage well below supply (for example < ~8–10 V under load) is a sign of a low heater circuit fault (vehicle-specific values vary)
Diagnostic algorithm
- Confirm active/stored P0031 and capture freeze frame/live data. Note if fault is intermittent or present continuously.
- Visually inspect Bank 1 Sensor 1 connector and wiring for corrosion, pin damage, rodent damage, melted insulation or water ingress.
- Check related fuses/relays. Replace any blown fuse and retest.
- With sensor disconnected, measure heater resistance across heater pins. Compare to manufacturer spec; infinite or very high resistance = bad sensor.
- Reconnect sensor. Backprobe heater supply and control pins with key ON and with ECM commanding heater ON (use a scan tool to command if possible). Verify supply voltage (should be near battery) and that control side is being driven (ground switching or voltage).
- If supply missing, trace supply back to fuse/relay and repair supply wiring. If control side stuck low (short to ground), isolate wiring to ECM and check for short to ground.
- If wiring and supply check good but heater still out of spec, replace the O2 sensor and clear codes. Retest drive cycle to confirm code does not return.
- If new sensor still reports heater low and wiring/supply are good, suspect ECM driver fault. Before ECM replacement, verify with professional bench/oscilloscope testing or manufacturer-specific diagnostics.
- After repairs, clear codes and perform a full drive cycle or required readiness routine to confirm repair.
Likely causes
- Failed O2 sensor (heater element open or high resistance)
- Damaged connector or wiring (corrosion, pin pushed out, water intrusion)
- Blown fuse for heater circuit
- Poor ground at sensor or battery supply wiring
Fault status
Status
Oxygen sensor heater control circuit low — Bank 1 Sensor 1. Check heater fuse, wiring/connectors, and sensor heater element; replace or repair as necessary.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
P0031
HUMMER
P — Powertrain
Heated Oxygen Sensor (HO2S) Heater Circuit Low Voltage Bank 1 Sensor 1
Views:
UK: 11
EN: 49
RU: 37
AI status
Completed
Completed
100%
Causes
- Blown fuse or relay for O2 sensor heater circuit
- Open or high-resistance wiring or connector (broken wire, corroded terminal)
- Short to ground in the heater control circuit
- Failed upstream (Bank 1 Sensor 1) oxygen sensor heater element
- Faulty ECM or driver transistor in ECM
- Incorrect or poor ground or battery supply to heater circuit
Symptoms
- Check Engine MIL/SES illuminated
- Longer than normal warm-up time and increased emissions until sensor reaches operating temperature
- Poor fuel economy or driveability during cold start
- Possible rich/lean fuel trim corrections while sensor cold
- No obvious engine misfire or performance loss once warmed (unless sensor entirely failed)
What to check
- Read and record freeze frame and live data (O2 sensor heater status, commanded heater state, fuel trims)
- Visual inspection of sensor connector and wiring for damage, corrosion or melted insulation
- Check fuse(s) and relays related to O2 sensor heaters
- Measure heater element resistance at sensor (with sensor disconnected) and compare to spec
- Backprobe connector with key on and heater commanded to ON to measure supply voltage and ground control
- Perform wiggle test on wiring while monitoring heater voltage/current or checking for intermittent faults
Signal parameters
- Heater supply voltage: battery voltage when commanded (approx. 11–14.5 V) — voltage significantly below battery when commanded can indicate low circuit
- Heater element resistance (ambient): typical range ~2–20 ohms (varies by sensor). Very high or infinite resistance = open heater
- Heater current when energized: roughly 0.5–2 A depending on sensor design (measured indirectly by voltage drop across known resistor or clamp meter)
- Expected ECU driver behavior: switches to ground (or supplies voltage) to energize heater — when commanded ON measured voltage at sensor connector should be near supply
- Trigger threshold: an open/high-resistance or measured voltage well below supply (for example < ~8–10 V under load) is a sign of a low heater circuit fault (vehicle-specific values vary)
Diagnostic algorithm
- Confirm active/stored P0031 and capture freeze frame/live data. Note if fault is intermittent or present continuously.
- Visually inspect Bank 1 Sensor 1 connector and wiring for corrosion, pin damage, rodent damage, melted insulation or water ingress.
- Check related fuses/relays. Replace any blown fuse and retest.
- With sensor disconnected, measure heater resistance across heater pins. Compare to manufacturer spec; infinite or very high resistance = bad sensor.
- Reconnect sensor. Backprobe heater supply and control pins with key ON and with ECM commanding heater ON (use a scan tool to command if possible). Verify supply voltage (should be near battery) and that control side is being driven (ground switching or voltage).
- If supply missing, trace supply back to fuse/relay and repair supply wiring. If control side stuck low (short to ground), isolate wiring to ECM and check for short to ground.
- If wiring and supply check good but heater still out of spec, replace the O2 sensor and clear codes. Retest drive cycle to confirm code does not return.
- If new sensor still reports heater low and wiring/supply are good, suspect ECM driver fault. Before ECM replacement, verify with professional bench/oscilloscope testing or manufacturer-specific diagnostics.
- After repairs, clear codes and perform a full drive cycle or required readiness routine to confirm repair.
Likely causes
- Failed O2 sensor (heater element open or high resistance)
- Damaged connector or wiring (corrosion, pin pushed out, water intrusion)
- Blown fuse for heater circuit
- Poor ground at sensor or battery supply wiring
Fault status
Status
Oxygen sensor heater control circuit low — Bank 1 Sensor 1. Check heater fuse, wiring/connectors, and sensor heater element; replace or repair as necessary.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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Code
P0031
LAND ROVER
P — Powertrain
Heated Oxygen Sensor Heater Control Circuit Low (bank 1 sensor 1)
Views:
UK: 5
EN: 51
RU: 34
AI status
Completed
Completed
100%
Causes
- Blown fuse or relay for O2 sensor heater circuit
- Open or high-resistance wiring or connector (broken wire, corroded terminal)
- Short to ground in the heater control circuit
- Failed upstream (Bank 1 Sensor 1) oxygen sensor heater element
- Faulty ECM or driver transistor in ECM
- Incorrect or poor ground or battery supply to heater circuit
Symptoms
- Check Engine MIL/SES illuminated
- Longer than normal warm-up time and increased emissions until sensor reaches operating temperature
- Poor fuel economy or driveability during cold start
- Possible rich/lean fuel trim corrections while sensor cold
- No obvious engine misfire or performance loss once warmed (unless sensor entirely failed)
What to check
- Read and record freeze frame and live data (O2 sensor heater status, commanded heater state, fuel trims)
- Visual inspection of sensor connector and wiring for damage, corrosion or melted insulation
- Check fuse(s) and relays related to O2 sensor heaters
- Measure heater element resistance at sensor (with sensor disconnected) and compare to spec
- Backprobe connector with key on and heater commanded to ON to measure supply voltage and ground control
- Perform wiggle test on wiring while monitoring heater voltage/current or checking for intermittent faults
Signal parameters
- Heater supply voltage: battery voltage when commanded (approx. 11–14.5 V) — voltage significantly below battery when commanded can indicate low circuit
- Heater element resistance (ambient): typical range ~2–20 ohms (varies by sensor). Very high or infinite resistance = open heater
- Heater current when energized: roughly 0.5–2 A depending on sensor design (measured indirectly by voltage drop across known resistor or clamp meter)
- Expected ECU driver behavior: switches to ground (or supplies voltage) to energize heater — when commanded ON measured voltage at sensor connector should be near supply
- Trigger threshold: an open/high-resistance or measured voltage well below supply (for example < ~8–10 V under load) is a sign of a low heater circuit fault (vehicle-specific values vary)
Diagnostic algorithm
- Confirm active/stored P0031 and capture freeze frame/live data. Note if fault is intermittent or present continuously.
- Visually inspect Bank 1 Sensor 1 connector and wiring for corrosion, pin damage, rodent damage, melted insulation or water ingress.
- Check related fuses/relays. Replace any blown fuse and retest.
- With sensor disconnected, measure heater resistance across heater pins. Compare to manufacturer spec; infinite or very high resistance = bad sensor.
- Reconnect sensor. Backprobe heater supply and control pins with key ON and with ECM commanding heater ON (use a scan tool to command if possible). Verify supply voltage (should be near battery) and that control side is being driven (ground switching or voltage).
- If supply missing, trace supply back to fuse/relay and repair supply wiring. If control side stuck low (short to ground), isolate wiring to ECM and check for short to ground.
- If wiring and supply check good but heater still out of spec, replace the O2 sensor and clear codes. Retest drive cycle to confirm code does not return.
- If new sensor still reports heater low and wiring/supply are good, suspect ECM driver fault. Before ECM replacement, verify with professional bench/oscilloscope testing or manufacturer-specific diagnostics.
- After repairs, clear codes and perform a full drive cycle or required readiness routine to confirm repair.
Likely causes
- Failed O2 sensor (heater element open or high resistance)
- Damaged connector or wiring (corrosion, pin pushed out, water intrusion)
- Blown fuse for heater circuit
- Poor ground at sensor or battery supply wiring
Fault status
Status
Oxygen sensor heater control circuit low — Bank 1 Sensor 1. Check heater fuse, wiring/connectors, and sensor heater element; replace or repair as necessary.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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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
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Workshop Manual199,00 UAH
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
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Code
P0031
MITSUBISHI
P — Powertrain
Oxygen sensor heater(front) low
Views:
UK: 11
EN: 52
RU: 36
AI status
Completed
Completed
100%
Causes
- Blown fuse or relay for O2 sensor heater circuit
- Open or high-resistance wiring or connector (broken wire, corroded terminal)
- Short to ground in the heater control circuit
- Failed upstream (Bank 1 Sensor 1) oxygen sensor heater element
- Faulty ECM or driver transistor in ECM
- Incorrect or poor ground or battery supply to heater circuit
Symptoms
- Check Engine MIL/SES illuminated
- Longer than normal warm-up time and increased emissions until sensor reaches operating temperature
- Poor fuel economy or driveability during cold start
- Possible rich/lean fuel trim corrections while sensor cold
- No obvious engine misfire or performance loss once warmed (unless sensor entirely failed)
What to check
- Read and record freeze frame and live data (O2 sensor heater status, commanded heater state, fuel trims)
- Visual inspection of sensor connector and wiring for damage, corrosion or melted insulation
- Check fuse(s) and relays related to O2 sensor heaters
- Measure heater element resistance at sensor (with sensor disconnected) and compare to spec
- Backprobe connector with key on and heater commanded to ON to measure supply voltage and ground control
- Perform wiggle test on wiring while monitoring heater voltage/current or checking for intermittent faults
Signal parameters
- Heater supply voltage: battery voltage when commanded (approx. 11–14.5 V) — voltage significantly below battery when commanded can indicate low circuit
- Heater element resistance (ambient): typical range ~2–20 ohms (varies by sensor). Very high or infinite resistance = open heater
- Heater current when energized: roughly 0.5–2 A depending on sensor design (measured indirectly by voltage drop across known resistor or clamp meter)
- Expected ECU driver behavior: switches to ground (or supplies voltage) to energize heater — when commanded ON measured voltage at sensor connector should be near supply
- Trigger threshold: an open/high-resistance or measured voltage well below supply (for example < ~8–10 V under load) is a sign of a low heater circuit fault (vehicle-specific values vary)
Diagnostic algorithm
- Confirm active/stored P0031 and capture freeze frame/live data. Note if fault is intermittent or present continuously.
- Visually inspect Bank 1 Sensor 1 connector and wiring for corrosion, pin damage, rodent damage, melted insulation or water ingress.
- Check related fuses/relays. Replace any blown fuse and retest.
- With sensor disconnected, measure heater resistance across heater pins. Compare to manufacturer spec; infinite or very high resistance = bad sensor.
- Reconnect sensor. Backprobe heater supply and control pins with key ON and with ECM commanding heater ON (use a scan tool to command if possible). Verify supply voltage (should be near battery) and that control side is being driven (ground switching or voltage).
- If supply missing, trace supply back to fuse/relay and repair supply wiring. If control side stuck low (short to ground), isolate wiring to ECM and check for short to ground.
- If wiring and supply check good but heater still out of spec, replace the O2 sensor and clear codes. Retest drive cycle to confirm code does not return.
- If new sensor still reports heater low and wiring/supply are good, suspect ECM driver fault. Before ECM replacement, verify with professional bench/oscilloscope testing or manufacturer-specific diagnostics.
- After repairs, clear codes and perform a full drive cycle or required readiness routine to confirm repair.
Likely causes
- Failed O2 sensor (heater element open or high resistance)
- Damaged connector or wiring (corrosion, pin pushed out, water intrusion)
- Blown fuse for heater circuit
- Poor ground at sensor or battery supply wiring
Fault status
Status
Oxygen sensor heater control circuit low — Bank 1 Sensor 1. Check heater fuse, wiring/connectors, and sensor heater element; replace or repair as necessary.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
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Send to email