O2 Sensor Circuit High Voltage (Bank 1, Sensor 1)
The upstream oxygen sensor signal is fixed at a high voltage, indicating either a continuously rich exhaust on bank 1 or a short to supply voltage in the signal circuit.
Affected components
- Oxygen sensor upstream
- Fuel injector
- Fuel pressure regulator
Common causes
- High likelihood: Genuine rich running (leaking injector, high fuel pressure)
- Medium likelihood: Signal wire shorted to supply voltage
- Low likelihood: Sensor poisoned by silicone or coolant
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.