AutoCodes – Nissan – P0138 2008 Nissan Maxima

P0138 2008 Nissan Maxima 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 2008 Nissan Maxima 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 4,384

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 Jun 14, 2020

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0138 2008 Nissan Maxima 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 2008 Nissan Maxima - HO2S12 Circuit High Voltage - AutoCodes.com — P0138 2008 Nissan Maxima Code - HO2S12 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P0138 2008 Nissan Maxima?

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 2008 Nissan Maxima?

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 2008 Nissan Maxima 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 2008 Nissan Maxima 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 2008 Nissan Maxima Code

1. What does the OBDII code P0138 on a 2008 Nissan Maxima mean?

This code indicates that the HO2S12 (Heated Oxygen Sensor 2 Bank 1 Sensor 2) circuit has detected high voltage.

2. What are the common symptoms of a P0138 code in a 2008 Nissan Maxima?

Common symptoms include poor fuel economy, rough idling, engine misfires, and the illumination of the Check Engine Light.

3. What are the possible causes of a P0138 code in a 2008 Nissan Maxima?

Causes can include a faulty HO2S12 sensor, wiring issues, exhaust leaks, engine vacuum leaks, or a problem with the engine's fuel system.

4. How can I diagnose a P0138 code in a 2008 Nissan Maxima?

Diagnosis typically involves checking the HO2S12 sensor's voltage readings, inspecting the sensor and its wiring for damage, and testing for exhaust or vacuum leaks.

5. Can I still drive my 2008 Nissan Maxima with a P0138 code?

It is not recommended to drive your vehicle with a P0138 code, as it can lead to decreased fuel efficiency and potential damage to the engine over time.

6. How can I fix a P0138 code on my 2008 Nissan Maxima?

Repair options may include replacing the HO2S12 sensor, repairing any damaged wiring, fixing exhaust leaks, addressing vacuum leaks, or repairing the fuel system.

7. Is it possible to reset a P0138 code in a 2008 Nissan Maxima without fixing the issue?

Resetting the code without addressing the underlying problem may temporarily turn off the Check Engine Light, but the issue will likely resurface.

8. How much does it typically cost to repair a P0138 code on a 2008 Nissan Maxima?

The cost of repairs can vary depending on the exact cause of the issue, but it may range from $100 to $300 for parts and labor.

9. Can a P0138 code on a 2008 Nissan Maxima cause other problems if left unfixed?

Leaving a P0138 code unresolved can potentially lead to reduced engine performance, increased emissions, and further damage to the vehicle's components over time.

10. How often should I check the HO2S12 sensor on my 2008 Nissan Maxima to prevent a P0138 code?

It's recommended to include the HO2S12 sensor in your regular vehicle maintenance schedule and have it inspected during routine service intervals to help prevent a P0138 code from occurring.