P0139 Mitsubishi Code - Cylinder 1-4 Heated Oxygen Rear Sensor Circuit Slow Response
Quick Answer
The Heated Oxygen Sensor 2 (HO2S), 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
- P0139 Mitsubishi indicates Cylinder 1-4 Heated Oxygen Rear Sensor Circuit Slow Response.
- 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 P0139 Mitsubishi Description
What are the Possible Causes of the DTC P0139 Mitsubishi?
- 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
- Inappropriate fuel pressure
- Faulty fuel injectors
- Intake air leaks may be faulty
- Exhaust gas leaks
How to Fix the DTC P0139 Mitsubishi?
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 P0139 Mitsubishi 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.
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Frequently Asked Questions about P0139 Mitsubishi Code
1. What does the OBDII code P0139 mean for a Mitsubishi vehicle?
The code P0139 indicates a slow response from the heated oxygen sensor located downstream of the catalytic converter for cylinders 1-4.
2. What are the common symptoms of P0139 in a Mitsubishi?
Symptoms may include reduced fuel efficiency, engine hesitation, rough idling, and an illuminated check engine light.
3. What causes the P0139 code to appear in a Mitsubishi?
Common causes include a failing rear oxygen sensor, exhaust leaks, damaged wiring or connectors, or a degraded catalytic converter.
4. Can a dirty or clogged catalytic converter trigger the P0139 code?
Yes, a clogged catalytic converter can affect exhaust flow and oxygen sensor readings, potentially triggering a slow response error.
5. How can I diagnose the P0139 code on my Mitsubishi?
Use an OBDII scanner to confirm the code, inspect the rear oxygen sensor and its wiring, and check for exhaust leaks or catalytic converter issues.
6. Is it safe to drive a Mitsubishi with the P0139 code?
While it may be possible to drive, prolonged use can lead to poor fuel economy and potentially damage other components, so repairs should be made promptly.
7. How do I fix the P0139 code on my Mitsubishi?
Repair steps may include replacing the rear oxygen sensor, fixing any exhaust leaks, repairing damaged wires or connectors, or replacing the catalytic converter if needed.
8. How much does it cost to repair code P0139 on a Mitsubishi?
Costs vary depending on the issue, but replacing an oxygen sensor typically costs $150-$300, while catalytic converter repairs can be significantly more expensive.
9. Can a P0139 code be triggered by bad fuel quality?
Poor fuel quality can lead to incomplete combustion, which may affect oxygen sensor readings and potentially trigger this code.
10. How can I prevent the P0139 code from appearing on my Mitsubishi?
Perform regular maintenance, use high-quality fuel, promptly address exhaust leaks, and replace oxygen sensors as recommended by the manufacturer.
Discuss the causes and fixes for P0139 Mitsubishi OBDII Code
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Does this code relate to others. I got this code immediately after replacing the downstream o2 censor and the catalysted converter. I was shooting the p0420 and p0138 codes before I did those repairs. And the very next morning got the p0139 on my way to the emissions testing site.
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What model and year is your vehicle? The P0139 code is for the dowstream O2 sensor as well. Double check the sensor connection and make sure there are no exhaust leaks.
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I have an 08 lancer (no turbo). It was taken to a shop for the previous repairs. Should it be something they’re responsible for? I only know how to drive cars.
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It's possible. There is only one rear Oxygen Sensor and both codes are for the same sensor.
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