P0139 Mercedes-Benz Code - O2 Sensor Circuit Slow Response Bank 1 Sensor 2
Quick Answer
The P0139 code for a Mercedes-Benz indicates that there is a slow response from the O2 sensor located in Bank 1 Sensor 2 of the vehicle's exhaust system. Common causes include Faulty O2 sensor, Wiring or connector issues, Exhaust leaks near the sensor. Severity is Moderate - service should be scheduled soon. The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.
- What it means
- P0139 Mercedes-Benz indicates O2 Sensor Circuit Slow Response Bank 1 Sensor 2.
- Common causes
- Common causes include Faulty O2 sensor, Wiring or connector issues, Exhaust leaks near the sensor.
- Severity
- Moderate - service should be scheduled soon.
- Can I drive?
- The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.
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Code P0139 Mercedes-Benz Description
The P0139 code for a Mercedes-Benz indicates that there is a slow response from the O2 sensor located in Bank 1 Sensor 2 of the vehicle's exhaust system. This sensor plays a crucial role in monitoring the oxygen levels in the exhaust gases and sending this information to the engine control module for proper fuel-air mixture adjustments. A slow response from this sensor can lead to incorrect fuel trim levels, affecting engine performance, fuel efficiency, and emissions output. If not addressed, it can result in reduced engine efficiency, increased emissions, and potential damage to other engine components over time.
Common Causes of P0139 Mercedes-Benz
- Faulty O2 sensor
- Wiring or connector issues
- Exhaust leaks near the sensor
- Contaminated sensor
- Engine misfires or other mechanical issues
Symptoms of P0139 Mercedes-Benz
- Decreased fuel efficiency
- Engine misfires or hesitations
- Rough idling or stalling
- Illuminated check engine light
- Failed emissions test
How to Fix P0139 Mercedes-Benz
- Diagnose the O2 sensor using a scan tool to confirm the P0139 code.
- Inspect the wiring and connectors for any damage or corrosion.
- Check for exhaust leaks near the sensor and repair if necessary.
- Replace the Bank 1 Sensor 2 O2 sensor if it is faulty or contaminated.
- Clear the code and perform a test drive to ensure the issue is resolved.
Cost to Fix P0139 Mercedes-Benz
The cost of repairing a P0139 code on a Mercedes-Benz can vary depending on the specific model and year of the vehicle, as well as the location of the repair. On average, replacing an O2 sensor can cost between $150 and $300 for parts, with additional labor costs ranging from $100 to $200. Overall, the total repair cost for this issue may fall between $250 and $500. It's recommended to contact local auto repair shops for accurate pricing information.
Tech Notes for P0139 Mercedes-Benz
Replacing the Rear Heated Oxygen Sensor Bank 1 usually takes care of the problem.
When is the Code Detected?
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Frequently Asked Questions about P0139 Mercedes-Benz Code
1. What does the OBDII code P0139 mean on a Mercedes-Benz?
P0139 indicates that the O2 Sensor Circuit Slow Response in Bank 1 Sensor 2 is not functioning as expected, suggesting that the sensor's response to changes in oxygen levels is slower than normal.
2. Where is Bank 1 Sensor 2 located on a Mercedes-Benz?
Bank 1 refers to the side of the engine that contains the first cylinder, and Sensor 2 is the oxygen sensor located downstream or after the catalytic converter.
3. What are common symptoms of the P0139 code in a Mercedes-Benz?
Symptoms include a check engine light, poor fuel economy, rough engine idle, and potentially a noticeable drop in engine performance.
4. What could cause the O2 sensor to respond slowly, triggering the P0139 code?
Causes could include a faulty oxygen sensor, exhaust leaks, damaged or corroded wiring or connectors, or a malfunctioning catalytic converter.
5. How can I fix the P0139 code on my Mercedes-Benz?
Repair strategies include replacing the faulty oxygen sensor, repairing any exhaust leaks, checking and repairing damaged wiring, and if necessary, replacing the catalytic converter.
6. Is it safe to drive my Mercedes-Benz with the P0139 code?
While you can typically still drive the vehicle, it is advisable to address the issue promptly as it can lead to increased emissions, reduced fuel efficiency, and potential damage to the catalytic converter.
7. How do I verify that the new O2 sensor has resolved the P0139 code on my Mercedes-Benz?
After replacing the sensor, clear the diagnostic trouble codes from your vehicle’s computer and drive the car for a while to see if the check engine light reappears and to ensure the repair was successful.
8. What tools are needed to diagnose and repair the P0139 code on a Mercedes-Benz?
Tools needed might include an OBDII code reader, digital multimeter, and basic hand tools to access and replace the oxygen sensor.
9. Could a P0139 code result from using low-quality fuel in my Mercedes-Benz?
While low-quality fuel might contribute to engine performance issues, it's unlikely to be a direct cause of a slow response from an O2 sensor. However, consistent use of poor-quality fuel can lead to engine deposits that might affect overall vehicle performance.
10. What is the cost implication of fixing the P0139 code in a Mercedes-Benz?
The cost primarily depends on whether you need to replace the sensor or perform additional repairs like fixing exhaust leaks or replacing the catalytic converter. Oxygen sensor replacement can range from $200 to $400 including parts and labor.
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