OBD-II · Engine and powertrain (P)
P0051
Oxygen sensor heater control circuit low bank 2 sensor 1
What it means
The heater control circuit of the upstream (before the catalytic converter) lambda sensor on bank 2 reads lower than expected, usually from an open heater, a missing supply or a short to ground. Confirm bank 2's location in the engine's service information.
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 | open heater element inside the sensor |
| 02 | blown fuse or missing power feed |
| 03 | control wire short to ground |
| 04 | broken wire or connector fault |
| 05 | ECU driver fault |
What to check, step by step
- 01Check the heater fuse and power feed: a missing supply reads as circuit low
- 02Measure the heater resistance: an open heater element is a common cause
- 03Check the ECU control wire for a short to ground or an open circuit
- 04Replace the sensor if the heater is open; repair wiring otherwise