Engine and gearbox (P)
P0031: O2 Sensor Heater Circuit Low
The oxygen sensor heater control circuit for bank 1, sensor 1 is reporting low voltage. This means the heater is not working properly, which can prevent the sensor from reaching its operating temperature.
Checked by a licensed car technician · last reviewed 30 September 2026
Symptoms
- Check engine light on
- Increased fuel consumption
- Rough idle
- Failed emissions test
Common causes
- Heater control wire shorted to ground
- Heater element internally shorted
- Corroded connector pins
How to check it yourself
- Inspect the wiring for damage or shorts
- Check the connector for corrosion or loose pins
- Test the heater element resistance with a multimeter
Can I keep driving?
The car can still be driven, but fuel efficiency may be reduced and emissions may increase.
General guidance, not a professional inspection. Confirm faults with measurements before buying parts, and use a qualified mechanic for brakes, steering, fuel leaks, airbags, and other safety-critical work. Terms and disclaimer