Upstream Bank 1 sensor voltage stuck high (rich / short to power).
SYMPTOMS
- Check-engine light
- Economy loss
- Drivability issues
LIKELY CAUSES
- Sensor failure
- Wiring short to power
- Rich fuel mixture
- Contamination
DIAGNOSIS STEPS
- Read sensor voltage
- Check wiring for short to power
- Verify fuel trims
RELATED PARTS
- Upstream O2 sensor