P0155 Oxygen sensor heater circuit (bank 2, sensor 1)
What P0155 means
The heater element inside the upstream oxygen sensor on bank 2 is not working, or its power or control circuit is broken. The sensor takes longer to start working after a cold start, so fuelling on that bank is less precise for longer. Bank 2 is the side of a V6, V8 or boxer engine that does not contain cylinder 1.
P0155 is a generic SAE J2012 code: it means the same on every make. The exact cause still depends on the car, so read the freeze-frame data before replacing parts.
At a glance
- Severity
- Medium
- Typical repair cost
- 60–350 €
- Workshop time
- 0.3–1.5 h
- Repair difficulty
- Easy
- DIY possible
- Yes
- Check engine light
- Yes
- Affects emissions test
- Yes
Parts and labour at an independent workshop in Europe. Main dealers charge more; the cause decides the bill, not the code.
Symptoms
- Check engine light on after several drives
- Slightly higher fuel consumption after cold starts
- Delayed switch to closed-loop fuel control
- Failed emissions inspection (oxygen sensor readiness)
Common causes
- Burnt-out heater element in the oxygen sensor
- Blown fuse or faulty relay in the heater supply
- Broken wire or corroded connector
- Engine control unit heater driver fault (rare)
Can I keep driving with P0155?
You can keep driving, but have it checked within one to two weeks. The usual fix is a new oxygen sensor.
What to check first
- Check the oxygen sensor heater fuse and relay.
- Inspect the bank 2 sensor connector and wiring for heat damage.
- Measure the heater resistance at the sensor; an open circuit means the heater has burnt out.
- Check supply voltage with the key on, then replace the sensor if the heater is open.
Related codes
- P0156 Oxygen sensor circuit (bank 2, sensor 2)
- P0153 Oxygen sensor slow response (bank 2 sensor 1)
- P0157 Oxygen sensor circuit low voltage (bank 2, sensor 2)
- P0152 Oxygen sensor circuit high voltage (bank 2, sensor 1)
- P0158 Oxygen sensor circuit high voltage (bank 2, sensor 2)
- P0151 Oxygen sensor circuit low voltage (bank 2, sensor 1)
- P0150 Oxygen sensor circuit (bank 2 sensor 1)
- P0160 Oxygen sensor circuit no activity detected (bank 2, sensor 2)
Data: TORKO fault-code catalogue, built on OBDex (CC0-1.0) and reviewed against workshop practice. Informational only — it does not replace a diagnosis by a mechanic.
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