OBD-II · Engine and powertrain (P)
P0155
Oxygen sensor heater circuit bank 2 sensor 1
What it means
The heater that brings the upstream (before the catalytic converter) lambda sensor on bank 2 up to working temperature is not working correctly. 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 | failed heater element inside the sensor |
| 02 | blown fuse |
| 03 | relay or power feed fault |
| 04 | wiring damage near the exhaust |
| 05 | connector corrosion |
What to check, step by step
- 01Check the fuse and relay that feed the lambda sensor heaters
- 02Measure the heater resistance at the sensor connector and compare with specification
- 03Check the heater power feed and the ECU control wire for opens or shorts
- 04Replace the sensor if the heater element is open or out of spec; the heater cannot be replaced separately