AutoCodes – Nissan – P0139 2009 Nissan Pathfinder

P0139 2009 Nissan Pathfinder Code - HO2S12 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 2009 Nissan Pathfinder indicates HO2S12 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.

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Code Popularity 2,278

How popular is this code, among other codes? Low

Repair Importance Level

Moderate (Service soon) (2 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Mar 25, 2024

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0139 2009 Nissan Pathfinder Description

The Heated Oxygen Sensor 2 (HO2S), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. For optimum catalyst operation, the air fuel mixture (air-fuel ratio) must be maintained near the ideal stoichiometric ratio. The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The Engine Control Module (ECM) adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric. The HO2S generates a voltage between 0.1 and 0.9 V in response to oxygen in the exhaust gas. If the oxygen in the exhaust gas increases, the air-fuel ratio becomes Lean. The ECM interprets Lean when the HO2S voltage is below 0.45 V. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. The ECM interprets Rich when the HO2S voltage is above 0.45 V.

OBDII Code P0139 2009 Nissan Pathfinder - HO2S12 Slow Response - AutoCodes.com — P0139 2009 Nissan Pathfinder Code - HO2S12 Slow Response

What does this mean?

What are the Possible Causes of the DTC P0139 2009 Nissan Pathfinder?

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 2009 Nissan Pathfinder?

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.

What does this mean?

Code Tech Notes

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

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0139 2009 Nissan Pathfinder 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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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 2009 Nissan Pathfinder Code

1. What does the OBDII code P0139 on a 2009 Nissan Pathfinder indicate?

- The code P0139 in a 2009 Nissan Pathfinder refers to a slow response from the HO2S12 sensor, also known as the downstream oxygen sensor.

2. What are common symptoms associated with the P0139 code in a 2009 Nissan Pathfinder?

- Common symptoms include decreased fuel efficiency, rough idling, engine misfires, and the illumination of the check engine light.

3. What are the possible causes of the P0139 code in a 2009 Nissan Pathfinder?

- Possible causes include a faulty HO2S12 sensor, wiring issues in the oxygen sensor circuit, exhaust leaks, or a problem with the engine's air-fuel mixture.

4. How can I diagnose the P0139 code in a 2009 Nissan Pathfinder?

- Diagnosis typically involves using an OBDII scanner to retrieve the code, inspecting the oxygen sensor wiring for damage, checking for exhaust leaks, and testing the sensor's response.

5. Can I continue driving my 2009 Nissan Pathfinder with the P0139 code?

- It is not recommended to drive the vehicle for an extended period with the P0139 code present, as it can lead to poor engine performance and potential damage over time.

6. How can I repair the P0139 code in a 2009 Nissan Pathfinder?

- Repair may involve replacing the HO2S12 sensor, repairing any damaged wiring, fixing exhaust leaks, or addressing issues with the air-fuel mixture as needed.

7. Is it possible to reset the check engine light after resolving the P0139 code in a 2009 Nissan Pathfinder?

- Yes, the check engine light can be reset using an OBDII scanner after the underlying issue triggering the P0139 code has been addressed.

8. How much does it typically cost to repair the P0139 code in a 2009 Nissan Pathfinder?

- The cost of repair can vary depending on the specific issue, but it may range from $100 to $300 for parts and labor, with sensor replacement being a common expense.

9. Are there any preventive measures to avoid the recurrence of the P0139 code in a 2009 Nissan Pathfinder?

- Regular maintenance, such as keeping up with scheduled tune-ups and addressing any engine performance issues promptly, can help prevent the reoccurrence of the P0139 code.

10. Can a DIY enthusiast fix the P0139 code in a 2009 Nissan Pathfinder?

- While some may attempt DIY repairs for the P0139 code, it is recommended to have the necessary tools, knowledge, and experience to properly diagnose and fix the issue to avoid further complications.