O2 Sensor Reference Voltage Circuit Low (Bank 1 Sensor 1)
The reference voltage feeding the bank 1, sensor 1 wide-band oxygen sensor is below the lower threshold. Often a short to ground in the wiring or a failed reference output stage.
Affected components
- Oxygen sensor upstream
- Oxygen sensor wiring
Common causes
- High likelihood: Reference line shorted to ground
- Low likelihood: ECU reference output failed
- Low likelihood: Connector pins corroded - high contact resistance
Possible symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
- A drive cycle may be required after repair
Related codes
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.