OBD2 code P0031: HO2S Heater Control Circuit Low (Bank 1 Sensor 1)
The upstream oxygen sensor on bank 1 (sensor 1, before the catalytic converter) only delivers a usable signal once its ceramic element is hot.
Detected Root Component
Powertrain Component
Observed Symptoms
- Check engine light on
- Closed-loop control starts late after a cold start
- Further heater codes if a shared fuse has blown
- Emissions test or readiness check failed
Possible Causes
- Heating element burnt out or high resistance (too little current)
- Supply wire interrupted or fuse blown
- Control wire to the engine control module interrupted
- Corroded connector with high contact resistance
- Output driver in the engine control module faulty
Tools Required
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Frequently asked questions about code P0031
What does code P0031 mean? ▾
OBD2 code P0031: HO2S Heater Control Circuit Low (Bank 1 Sensor 1). The upstream oxygen sensor on bank 1 (sensor 1, before the catalytic converter) only delivers a usable signal once its ceramic element is hot.
What are the symptoms of code P0031? ▾
Code P0031 may cause: Check engine light on, Closed-loop control starts late after a cold start, Further heater codes if a shared fuse has blown, Emissions test or readiness check failed. The intensity of these symptoms varies depending on the vehicle and driving conditions.
What causes code P0031? ▾
The most common causes of code P0031 are: Heating element burnt out or high resistance (too little current), Supply wire interrupted or fuse blown, Control wire to the engine control module interrupted, Corroded connector with high contact resistance. A proper OBD2 diagnostic will pinpoint the exact cause.
Is it serious to drive with code P0031? ▾
Code P0031 has moderate severity (Warning). Short-term driving remains possible, but a prompt check is recommended to prevent worsening.
How do I fix code P0031? ▾
Start by reading the code with an OBD2 scanner, then follow the interactive decision tree on this page. Priority causes to check: Heating element burnt out or high resistance (too little current), Supply wire interrupted or fuse blown, Control wire to the engine control module interrupted, Corroded connector with high contact resistance. Difficulty: Medium · Estimated time: 30-60min.