P0138 Mercedes-Benz Code - O2 Sensor Circuit High Voltage Bank 1 Sensor 2
Quick Answer
The Heated Oxygen Sensor 2 (HO2S) (Rear O2 Sensor), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. Common causes include Faulty Rear Heated Oxygen Sensor Bank 1, Rear Heated Oxygen Sensor Bank 1 harness is open or shorted, Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection. 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
- P0138 Mercedes-Benz indicates O2 Sensor Circuit High Voltage Bank 1 Sensor 2.
- Common causes
- Common causes include Faulty Rear Heated Oxygen Sensor Bank 1, Rear Heated Oxygen Sensor Bank 1 harness is open or shorted, Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection.
- 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.
Code P0138 Mercedes-Benz Description
What are the Possible Causes of the DTC P0138 Mercedes-Benz?
- Faulty Rear Heated Oxygen Sensor Bank 1
- Rear Heated Oxygen Sensor Bank 1 harness is open or shorted
- Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection
- Intake air leaks
- Exhaust gas leaks
- Inappropriate fuel pressure
- Faulty fuel injectors
How to Fix the DTC P0138 Mercedes-Benz?
Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.
Code Tech Notes
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the P0138 Mercedes-Benz code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.
Need more information about the P0138 Mercedes-Benz code?
Need more information on how to fix the P0138 Mercedes-Benz code? Get Access to Factory Service Manuals
Need Help with the Code?
Get the P0138 Mercedes-Benz code diagnosed by a professional: Find a repair shop in your area
Frequently Asked Questions about P0138 Mercedes-Benz Code
1. What does OBDII code P0138 on a Mercedes-Benz mean?
- It indicates a high voltage in the O2 sensor circuit of Bank 1 Sensor 2.
2. What are the common symptoms of OBDII code P0138 in a Mercedes-Benz?
- Symptoms may include poor fuel economy, rough idle, engine hesitation, and an illuminated check engine light.
3. What can cause the O2 sensor circuit high voltage error (P0138) in a Mercedes-Benz?
- Possible causes include a faulty O2 sensor, wiring issues, exhaust leaks, or a problem with the engine's air-fuel mixture.
4. How can I diagnose the O2 sensor circuit high voltage error in my Mercedes-Benz?
- A professional diagnostic scan tool can help pinpoint the exact cause of the issue by reading live data from the O2 sensor.
5. Can I continue driving my Mercedes-Benz with the P0138 error code?
- It's not recommended to drive for an extended period with this code as it can affect the engine's performance and emissions.
6. How do I repair the O2 sensor circuit high voltage error in my Mercedes-Benz?
- The repair may involve replacing the faulty O2 sensor, repairing damaged wiring, fixing exhaust leaks, or addressing issues with the air-fuel mixture.
7. Is it possible to reset the P0138 code on a Mercedes-Benz without fixing the underlying issue?
- While you can clear the code temporarily, it will likely return until the root cause is identified and repaired.
8. Can a DIY enthusiast fix the O2 sensor circuit high voltage error in a Mercedes-Benz?
- Depending on your skill level and access to tools, you may be able to replace the O2 sensor yourself, but diagnosing the exact issue is best left to professionals.
9. How much does it cost to repair the P0138 code in a Mercedes-Benz?
- The cost of repair can vary widely based on the specific issue, location, and labor rates, but it's best to get a professional estimate.
10. How often should the O2 sensors be checked and replaced in a Mercedes-Benz to prevent the P0138 code?
- O2 sensors typically last around 100,000 miles, but regular maintenance and inspections can help detect issues early and prevent codes like P0138.
Discuss the causes and fixes for P0138 Mercedes-Benz OBDII Code
Code P0138 Mercedes-Benz comments
No comments found for this page.
Fix Your Car Smarter
Try the New AutoCodes App!
Get complete OBDII diagnostics, repair solutions, and cost estimates, plus AI chat support on demand.
