OBD-II · Engine and powertrain (P)
P0038
Oxygen sensor heater control circuit high bank 1 sensor 2
What it means
The heater control circuit of the downstream (after the catalytic converter) lambda sensor on bank 1 reads higher than expected, usually from a short to battery voltage or a shorted heater.
Symptoms
- engine warning light
- slightly higher fuel consumption and emissions after a cold start
- usually no change in how the car drives
Likely causes, most likely first
| No. | Cause |
|---|---|
| 01 | control wire short to battery voltage |
| 02 | internally shorted heater element |
| 03 | water or damage in the connector |
| 04 | ECU driver fault |
What to check, step by step
- 01Check the ECU control wire for a short to battery voltage
- 02Measure the heater resistance: an internally shorted heater draws too much current
- 03Inspect the connector for water or melted pins
- 04Replace the sensor if the heater is out of spec; repair wiring otherwise