P0135 Oxygen sensor heater circuit (bank 1, sensor 1)
What P0135 means
The heater element inside the upstream oxygen sensor on bank 1 is not working, or its power or control circuit is broken. The sensor then needs much longer to reach working temperature, so the engine runs on its cold map for longer after each start.
P0135 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 (most common)
- 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 P0135?
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 connector and wiring for damage near the exhaust.
- Measure the heater resistance at the sensor connector; 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
- P0134 Oxygen sensor circuit no activity detected (bank 1, sensor 1)
- P0136 Oxygen sensor circuit (bank 1, sensor 2)
- P0133 Oxygen sensor slow response (bank 1 sensor 1)
- P0137 Oxygen sensor circuit low voltage (bank 1, sensor 2)
- P0132 Oxygen sensor circuit high voltage (bank 1, sensor 1)
- P0138 Oxygen sensor circuit high voltage (bank 1, sensor 2)
- P0131 Oxygen sensor circuit low voltage (bank 1, sensor 1)
- P0139 Oxygen sensor circuit slow response (bank 1, 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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