P0036low severityPowertrain
HO2S Heater Control Circuit Bank 1 Sensor 2
on 2003 BMW 525iT E39 2.5L I6 M54 Touring · RWD
What this code means
The PCM detected a malfunction in the heater circuit of the downstream heated oxygen sensor (Bank 1, Sensor 2).
Symptoms
- Check Engine Light
- Failed emissions test
- Poor catalyst monitoring
Common causes
- Faulty O2 sensor heater
- Blown fuse
- Wiring issue
Diagnostic steps
- Check fuse
- Test heater resistance
- Inspect wiring
- Check PCM output
Repair notes
Replace downstream O2 sensor or repair wiring.
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