P0057HO2S Heater Control Circuit Low (Bank 2 Sensor 2)
What it means
The voltage on the heater control circuit is too low: usually the control wire is shorted to ground or the heater supply is missing. Without the heater the sensor takes longer to work after a cold start.
Symptoms
- Check engine light
- Slightly higher fuel use after cold starts
- Usually no change in how the car drives
Common causes
- Open heater element inside the oxygen sensor
- Blown heater fuse or missing 12 V supply
- Damaged wiring near the exhaust
- ECU heater driver fault
What to check first
- Measure the heater resistance at the sensor (typically 3–15 Ω, check the specification)
- Check the 12 V supply with the key on
- Check the control (ground) side from the ECU with a test lamp or scope
Generic OBD-II meaning. Manufacturer-specific meanings and checks can differ; always check the service information for the car.