No signal activity from the upstream Bank 1 O2 sensor (open circuit / dead sensor).
SYMPTOMS
- Check-engine light
- Economy loss
- Drivability issues
LIKELY CAUSES
- Dead O2 sensor
- Open circuit in wiring
- Failed sensor heater
- Exhaust leak
DIAGNOSIS STEPS
- Check sensor signal and heater
- Test wiring continuity
- Inspect for exhaust leaks
- Replace sensor
RELATED PARTS
- Upstream O2 sensor