P0138 O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)
The downstream (after the catalytic converter) oxygen sensor, Bank 1 Sensor 2, stays at high voltage, which reads as rich.
Common causes
- Rich running from leaking injector or high fuel pressure
- Faulty sensor
- Signal shorted to voltage
Symptoms
- Check engine light
- Fuel smell from exhaust
What to check
- Check fuel trims and fuel pressure
- Inspect wiring
- Replace sensor if contaminated
Manufacturers may add their own detail to generic codes. If your vehicle shows a different description for P0138, follow the service information for that make and model.
Related codes
- P0130 O2 Sensor Circuit (Bank 1 Sensor 1)
- P0131 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)
- P0132 O2 Sensor Circuit High Voltage (Bank 1 Sensor 1)
- P0133 O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)
- P0134 O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)
- P0135 O2 Sensor Heater Circuit (Bank 1 Sensor 1)