OBD codes / P0138
P0138
ModerateO2 Sensor Circuit High Voltage (Bank 1, Sensor 2)
Get it looked at soon to avoid further wear.
Likely causes
- failing downstream O2 sensor
- short to voltage
- contaminated sensor
Common fixes
- replace the rear O2 sensor
- inspect the wiring
Seeing P0138 on your car? Get a diagnosis specific to your exact year, make and model.
Diagnose P0138 for my vehicleGeneric OBD-II reference. Manufacturer-specific behavior varies — confirm with a scan tool and, for safety-related codes, a professional inspection.