Upstream Bank 1 O2 sensor heater circuit voltage low.
SYMPTOMS
- Check-engine light
- Drivability or performance issues
LIKELY CAUSES
- Faulty O2 sensor heater
- Short to ground in the signal wire
- Open ground or corroded connector
- ECM/PCM fault (rare)
DIAGNOSIS STEPS
- Inspect the O2 sensor heater wiring and connector
- Check the signal circuit for a short to ground
- Verify reference voltage and ground
- Compare live data to expected
- Replace the component if confirmed faulty
RELATED PARTS
- Upstream O2 sensor