Engine and gearbox (P)
P0043: HO2S Heater Control Circuit Low
The heater control circuit for the oxygen sensor on bank 1, sensor 3, is receiving a voltage lower than expected. This may be due to a short to ground or a low-resistance fault.
Checked by a licensed car technician · last reviewed 30 September 2026
Symptoms
- Check engine light on
- Poor fuel economy
- Failed emissions test
- Rough idle
Common causes
- Heater wiring shorted to ground
- Connector pins corroded
- Harness chafing through insulation
How to check it yourself
- Inspect the wiring for damage or chafing
- Check the connector for corrosion or damage
- Test the sensor's resistance with a multimeter
Can I keep driving?
The car can still be driven, but it may run inefficiently and fail emissions tests.
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