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P0139 2005 Nissan Pathfinder Code - HO2S12 Slow Response

Quick Answer

The P0139 diagnostic trouble code (DTC) for a 2005 Nissan Pathfinder refers to a slow response from the downstream oxygen sensor (HO2S12). Common causes include Faulty downstream oxygen sensor, Wiring or connector issues in the oxygen sensor circuit, Exhaust leaks near the oxygen 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 2005 Nissan Pathfinder indicates HO2S12 Slow Response.
Common causes
Common causes include Faulty downstream oxygen sensor, Wiring or connector issues in the oxygen sensor circuit, Exhaust leaks near the oxygen 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.
What is this?
Table of contents Created and updated by William Orellana on Sep 13, 2024
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Code P0139 2005 Nissan Pathfinder Description

The P0139 diagnostic trouble code (DTC) for a 2005 Nissan Pathfinder refers to a slow response from the downstream oxygen sensor (HO2S12). The oxygen sensor is a crucial component of the vehicle's emissions control system, as it measures the amount of oxygen in the exhaust gases to help the engine control module (ECM) adjust the air-fuel mixture for optimal combustion. A slow response from the oxygen sensor can lead to inaccurate readings and affect the engine's performance and fuel efficiency.

OBDII Code P0139 2005 Nissan Pathfinder - HO2S12 Slow Response
P0139 2005 Nissan Pathfinder Code - HO2S12 Slow Response

Common Causes of P0139 2005 Nissan Pathfinder

  1. Faulty downstream oxygen sensor
  2. Wiring or connector issues in the oxygen sensor circuit
  3. Exhaust leaks near the oxygen sensor
  4. Contaminated or damaged oxygen sensor
  5. ECM software or hardware issues

Symptoms of P0139 2005 Nissan Pathfinder

  1. Check engine light illuminated on the dashboard
  2. Decreased fuel efficiency
  3. Rough idling or stalling
  4. Engine misfires
  5. Increased emissions

How to Fix P0139 2005 Nissan Pathfinder

  1. Diagnose the issue by using a scan tool to retrieve the DTC and inspect the downstream oxygen sensor and its wiring.
  2. Replace the downstream oxygen sensor if it is faulty or contaminated.
  3. Check and repair any wiring or connector issues in the oxygen sensor circuit.
  4. Inspect for exhaust leaks near the oxygen sensor and repair as necessary.
  5. Clear the DTC from the ECM memory and perform a test drive to ensure the issue has been resolved.

Cost to Fix P0139 2005 Nissan Pathfinder

The typical repair costs for addressing a P0139 code on a 2005 Nissan Pathfinder can vary depending on the specific cause of the issue. In general, replacing a downstream oxygen sensor can cost between $100 and $300 for the part, with additional labor costs ranging from $100 to $200. Keep in mind that diagnostic time and labor rates at auto repair shops can vary, so it's advisable to check with local shops for a more accurate estimate based on your location and vehicle specifics.

What does this mean?

Tech Notes for P0139 2005 Nissan Pathfinder

Replacing the Rear Heated Oxygen Sensor Bank 1 usually takes care of the problem.

When is the Code Detected?

The P0139 code is set when the Engine Control Module (ECM) detects that the rear O2 sensor takes more time to respond between rich and lean than the specified time.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0139 2005 Nissan Pathfinder Code

1. What does OBDII code P0139 on a 2005 Nissan Pathfinder mean?

The code P0139 indicates a slow response from the downstream oxygen sensor (HO2S12) located after the catalytic converter.

2. What are some common symptoms of HO2S12 slow response in a 2005 Nissan Pathfinder?

Common symptoms of a slow response from the downstream oxygen sensor may include poor fuel economy, rough idling, engine misfires, and a noticeable decrease in overall vehicle performance.

3. What are the possible causes of OBDII code P0139 on a 2005 Nissan Pathfinder?

Potential causes of code P0139 include a faulty downstream oxygen sensor, wiring issues in the oxygen sensor circuit, exhaust leaks, a damaged catalytic converter, or an engine running too rich or too lean.

4. How can I diagnose the HO2S12 slow response issue on my 2005 Nissan Pathfinder?

To diagnose the slow response from the downstream oxygen sensor, you can use an OBDII scanner to retrieve the exact trouble code, visually inspect the sensor and its wiring for any damage, and perform a voltage test to check sensor operation.

5. Can I still drive my 2005 Nissan Pathfinder with OBDII code P0139?

It is generally not recommended to drive your vehicle with an unresolved HO2S12 slow response issue, as it can lead to further damage to the catalytic converter and other engine components. It's best to address the problem promptly.

6. How do I repair OBDII code P0139 on my 2005 Nissan Pathfinder?

Repairing code P0139 may involve replacing the downstream oxygen sensor (HO2S12), repairing any damaged wiring in the sensor circuit, addressing exhaust leaks, and ensuring proper engine performance to prevent the issue from reoccurring.

7. Can a DIY enthusiast fix OBDII code P0139 on a 2005 Nissan Pathfinder?

While some experienced DIY enthusiasts may be able to replace the downstream oxygen sensor and perform basic checks, diagnosing and repairing the underlying causes of a slow response from the sensor may require professional expertise and specialized tools.

8. How much does it cost to repair OBDII code P0139 on a 2005 Nissan Pathfinder?

The cost of repairing code P0139 can vary depending on the specific issue causing the slow response from the downstream oxygen sensor. Expenses may include the cost of a new sensor, labor charges, and any additional parts or repairs needed.

9. Will resetting the OBDII code P0139 on my 2005 Nissan Pathfinder make it go away permanently?

Simply resetting the trouble code without addressing the root cause of the slow response from the downstream oxygen sensor will likely result in the code reappearing once the vehicle is driven again. It is essential to diagnose and fix the underlying issue for a permanent solution.

10. How often should I have the downstream oxygen sensor checked on my 2005 Nissan Pathfinder to prevent OBDII code P0139?

Regular maintenance checks, particularly during scheduled service intervals, can help catch potential issues with the downstream oxygen sensor early on. It's advisable to have the sensor inspected as part of routine vehicle maintenance to prevent code P0139 and related problems.

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