O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)
Common Symptoms
- Check engine light on
- Catalyst monitor may not complete
- No significant drivability symptoms
Most Likely Root Causes
- Failed downstream O2 sensor heater
- Open heater circuit wiring
- Blown heater fuse
- PCM heater driver failure
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Severity / Derate Risk
Low.
Component Location
Bank 1 Sensor 2 (downstream) — after catalytic converter, Bank 1 side.
Manufacturer Notes
Downstream sensor heater failure often prevents catalyst efficiency monitor from completing. May cause P0420 to set indirectly.
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