AutoCodes – Nissan – P0138 2005 Nissan Altima Sedan

P0138 2005 Nissan Altima Sedan 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 Altima Sedan 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 7,237

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

What does this mean?

What are the Possible Causes of the DTC P0138 2005 Nissan Altima Sedan?

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 Altima Sedan?

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 Altima Sedan 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 2005 Nissan Altima Sedan Code

1. What are the common symptoms of OBDII code P0138 in a 2005 Nissan Altima Sedan?

- The common symptoms include poor fuel economy, rough idling, engine misfires, and the illumination of the check engine light.

2. What does the OBDII code P0138 for a 2005 Nissan Altima Sedan indicate?

- The code P0138 indicates that the HO2S12 sensor circuit has detected high voltage levels, which may point to a problem with the oxygen sensor or the wiring.

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

- The possible causes include a faulty oxygen sensor (HO2S12), damaged wiring or connectors, exhaust system leaks, engine misfires, or issues with the engine's fuel system.

4. How can I diagnose the OBDII code P0138 in my 2005 Nissan Altima Sedan?

- You can diagnose the code by inspecting the oxygen sensor and its wiring for any visible damage, checking for exhaust leaks, performing a voltage test on the sensor, and using a scan tool to monitor sensor data.

5. What are the repair options for resolving OBDII code P0138 on a 2005 Nissan Altima Sedan?

- The repair options may include replacing the HO2S12 sensor, repairing or replacing damaged wiring or connectors, fixing any exhaust leaks, addressing engine misfires, or troubleshooting the fuel system.

6. Can I drive my 2005 Nissan Altima Sedan with the OBDII code P0138?

- It is not recommended to drive the vehicle for an extended period with the code P0138 illuminated, as it can lead to poor engine performance and potentially cause damage to the catalytic converter.

7. How much does it typically cost to repair OBDII code P0138 on a 2005 Nissan Altima Sedan?

- The cost of repair can vary depending on the exact cause of the code, but it may range from $100 to $300 for parts and labor, excluding any additional diagnostic fees.

8. Will resetting the check engine light clear the OBDII code P0138 in my 2005 Nissan Altima Sedan?

- Resetting the check engine light may temporarily turn it off, but it will not fix the underlying issue causing the code. It is recommended to diagnose and address the problem to prevent it from recurring.

9. Can a DIY enthusiast fix OBDII code P0138 on a 2005 Nissan Altima Sedan?

- Depending on their skill level and access to tools, a DIY enthusiast may be able to address simpler causes of the code, such as replacing the oxygen sensor or repairing wiring. However, more complex issues may require professional assistance.

10. How often does the HO2S12 sensor need to be replaced in a 2005 Nissan Altima Sedan?

- The oxygen sensor (HO2S12) typically has a lifespan of around 60,000 to 100,000 miles. However, factors like driving conditions and maintenance practices can affect its longevity.