P0139 OBD-II: O2 Sensor Circuit Slow Response
P0139 Severity
Will P0139 go away on its own?
Once the vehicle's onboard system no longer detects the issue, most codes will disappear on their own. If your vehicle still has this code, however, it should be properly diagnosed to avoid a more serious problem.
For a proper diagnosis, RepairPal Certified shops have the equipment, tools, and expertise.
Moderate severity codes might not threaten the vehicle's safety or functionality immediately, but you should still get it diagnosed within a reasonable time frame to keep your car running well.
What causes OBD-II fault code P0139?
The purpose of the oxygen sensor is to measure the oxygen content in the exhaust gases after they leave the combustion process of the engine. This information is critical to the PCM's ability to maintain efficient fuel economy. When the PCM detects a failure of the sensor or the information received from the sensor, it will set code P0139.
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OBD II Fault Code
- OBD II P0139
Fault Code Definition
When the up and down "cross-counting" voltage activity from the Oxygen Sensor is too slow, code P0139 is triggered and the Check Engine/Service Engine Soon Light will illuminate.
P0139 Symptoms
- Check Engine Light will illuminate
- In many cases, no abnormal symptoms may be noticed
- In some cases, the vehicle will fail an Emissions Test
- In some cases, the engine may "ping" and produce excess NOx
Common Problems That Trigger the P0139 Code
- Defective Catalytic Converter
- Faulty Rear Oxygen Sensor wiring or connections
Common Misdiagnoses
- Oxygen Sensor Sensor is replaced when the problem is a defective Catalytic Converter
- Oxygen Sensor is replaced when the problem is faulty sensor wiring or connections
- Oxygen Sensor is replaced when the problem is an exhaust leak in front of the Oxygen Sensor
Ask our experts about P0139.
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