The post-catalyst (rear) O2 sensor on Bank 1 reports a persistently rich condition.
SYMPTOMS
- Check-engine light
- Possible rough idle
- Worse economy
LIKELY CAUSES
- Failing downstream O2 sensor
- Fuel delivery issue
- Contaminated sensor
- Leaking injector
DIAGNOSIS STEPS
- Check downstream O2 data
- Verify fuel pressure and trims
- Inspect for injector leakage
RELATED PARTS
- Rear O2 sensor