P0138 P0138 OBD-II: O2 Sensor Circuit High Voltage
What P0138 means for you
The code indicates a significant issue with the oxygen sensor circuit, which can affect vehicle performance and emissions.
Symptoms
- The Check Engine Light will turn on.
- The vehicle may experience rough idling or performance issues.
- Fuel efficiency may decline.
- Exhaust may emit a foul odor.
- In rare instances, the driver may not notice any symptoms.
Common causes
- The oxygen sensor's role is to assess the oxygen levels in the exhaust gases after combustion, which is essential for the engine control module (PCM) to optimize fuel efficiency. If the PCM identifies a malfunction with the sensor or the data it receives, it triggers code P0138.
Tune it yourself
Buy a tuning tool and start remapping P0138 for your customers. We provide the accessories and the file. You keep the profit.
Start tuning
Or send us your ECU
Prefer we handle it? Send your ECU straight to us and we’ll fix it for you.
Send your ECUWhat this code means
Code P0138 signifies that the oxygen sensor circuit is registering a high voltage condition. This can lead to improper fuel mixture adjustments and increased emissions, as the PCM relies on accurate readings from the sensor to manage engine performance effectively.
How a workshop diagnoses it
1. Use a quality scan tool to check for freeze frame data when the code was set. 2. Conduct a test drive to replicate the conditions that triggered the code, monitoring load, speed, and RPM. 3. Visually inspect the oxygen sensor and its connections for any damage or disconnections. 4. Verify the presence of 12-volt heater signals and proper grounding at the sensor. 5. Use a Digital Volt Ohm Meter (DVOM) to check the signal from the sensor to the PCM.
Frequently asked questions
It is not advisable to continue driving with a P0138 code, as it may lead to reduced fuel efficiency and increased emissions.
The cost to repair a P0138 code can vary, but replacing the oxygen sensor typically ranges from $100 to $300, depending on the vehicle make and model.
Common symptoms include an illuminated Check Engine Light, rough idling, decreased fuel economy, and bad-smelling exhaust.
