AutoCodes – Nissan – P0138 2007 Nissan Maxima

P0138 2007 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 2007 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 4,937

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 2007 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 2007 Nissan Maxima - HO2S12 Circuit High Voltage - AutoCodes.com — P0138 2007 Nissan Maxima Code - HO2S12 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P0138 2007 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 2007 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 2007 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.

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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 2007 Nissan Maxima Code

1. What does the OBDII code P0138 mean on a 2007 Nissan Maxima?

The P0138 code indicates that the Oxygen Sensor (O2) in bank 1, sensor 2, is experiencing high voltage output. This sensor is located after the catalytic converter.

2. What are common symptoms of code P0138 in a 2007 Nissan Maxima?

Symptoms include a check engine light, poor fuel economy, and possibly a rough engine idle.

3. What can cause the P0138 code to appear on a 2007 Nissan Maxima?

Causes may include a faulty oxygen sensor, wiring issues related to the O2 sensor (like shorts to voltage), or a problem with the engine's fuel management system.

4. How can I fix the P0138 code on my 2007 Nissan Maxima?

Repairs can involve replacing the oxygen sensor, repairing any damaged wiring or connectors, and checking the fuel pressure and other related engine management components.

5. Is it safe to drive my 2007 Nissan Maxima with the P0138 code?

While you can drive the vehicle, prolonged driving with this issue can lead to inefficiencies in fuel consumption, potential damage to the catalytic converter, or other engine problems.

6. How do I confirm that the oxygen sensor is the problem with a P0138 code in a 2007 Nissan Maxima?

Confirming the issue typically involves using an OBDII scanner to check the oxygen sensor's voltage output and ensure it is consistently higher than normal. You might also perform a visual inspection of the sensor and surrounding wiring.

7. Could the P0138 code be triggered by something other than the oxygen sensor in a 2007 Nissan Maxima?

Yes, it could also be triggered by issues with the catalytic converter, exhaust leaks, or problems in the engine control module, although these are less common.

8. What is the cost to repair the P0138 code in a 2007 Nissan Maxima?

The cost largely depends on the specific repair needed. Oxygen sensor replacement can range from $200 to $400 including parts and labor, but costs can vary based on location and the service provider.

9. How urgent is it to address the P0138 code in a 2007 Nissan Maxima?

It is advisable to address it soon. Delaying repairs can lead to more significant issues like a failed catalytic converter, which is a much more costly repair.

10. Can a malfunctioning oxygen sensor due to P0138 affect the performance of a 2007 Nissan Maxima?

Yes, a malfunctioning sensor can affect engine performance, fuel efficiency, and emissions. It may cause the engine to run rich (more fuel than needed), leading to higher emissions and reduced performance.