AutoCodes – Nissan – P0138 2005 Nissan Pathfinder

P0138 2005 Nissan Pathfinder Code - HO2S12 Circuit High Voltage

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 2005 Nissan Pathfinder indicates HO2S12 Circuit High Voltage.
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 7,035

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 P0138 2005 Nissan Pathfinder Description

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. 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 P0138 2005 Nissan Pathfinder - HO2S12 Circuit High Voltage - AutoCodes.com — P0138 2005 Nissan Pathfinder Code - HO2S12 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P0138 2005 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
Intake air leaks
Exhaust gas leaks
Inappropriate fuel pressure
Faulty fuel injectors

How to Fix the DTC P0138 2005 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 P0138 2005 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.

Need more information about the P0138 2005 Nissan Pathfinder code?

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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 P0138 2005 Nissan Pathfinder Code

1. What does OBDII code P0138 on a 2005 Nissan Pathfinder mean?

- OBDII code P0138 for a 2005 Nissan Pathfinder indicates a high voltage condition in the HO2S12 (Heated Oxygen Sensor Bank 1 Sensor 2) circuit.

2. What are the common symptoms of OBDII code P0138 on a 2005 Nissan Pathfinder?

- Common symptoms of code P0138 may include poor fuel economy, rough idling, engine hesitation, or the illumination of the Check Engine Light.

3. What are the possible causes of OBDII code P0138 on a 2005 Nissan Pathfinder?

- The main causes of code P0138 can be a faulty oxygen sensor, a damaged or shorted wiring harness, or an issue with the vehicle's engine control module (ECM).

4. How can I diagnose OBDII code P0138 on my 2005 Nissan Pathfinder?

- To diagnose code P0138, you can use an OBDII scanner to retrieve the code, visually inspect the oxygen sensor and its wiring, and perform voltage tests on the sensor.

5. Can I drive my 2005 Nissan Pathfinder with OBDII code P0138?

- It is not recommended to drive your vehicle with code P0138 unresolved, as it can lead to decreased fuel efficiency and potential damage to the catalytic converter.

6. How do I repair OBDII code P0138 on my 2005 Nissan Pathfinder?

- Repairing code P0138 may involve replacing the HO2S12 sensor, repairing or replacing damaged wiring, or resetting the ECM after resolving the underlying issue.

7. Are there any DIY tips for fixing OBDII code P0138 on a 2005 Nissan Pathfinder?

- DIY tips for addressing code P0138 include checking for loose connections, ensuring the sensor is securely mounted, and carefully following the manufacturer's repair procedures.

8. How much does it cost to fix OBDII code P0138 on a 2005 Nissan Pathfinder?

- The cost of fixing code P0138 can vary depending on the root cause, but it may range from $100 to $300 for parts and labor if the oxygen sensor needs replacement.

9. Will resetting the Check Engine Light resolve OBDII code P0138 on a 2005 Nissan Pathfinder?

- Resetting the Check Engine Light without addressing the underlying issue causing code P0138 will not fix the problem; it is essential to diagnose and repair the root cause.

10. Can a mechanic help me with OBDII code P0138 on my 2005 Nissan Pathfinder?

- Yes, a qualified mechanic can diagnose and repair code P0138 on your 2005 Nissan Pathfinder by using specialized tools and expertise to resolve the high voltage issue in the HO2S12 circuit.