AutoCodes – Nissan – P0138 2008 Nissan Altima Sedan

P0138 2008 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 2008 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 9,112

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 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 2008 Nissan Altima Sedan - HO2S12 Circuit High Voltage - AutoCodes.com — P0138 2008 Nissan Altima Sedan Code - HO2S12 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P0138 2008 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 2008 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 2008 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 2008 Nissan Altima Sedan Code

1. What are the common symptoms of OBDII code P0138 on a 2008 Nissan Altima Sedan?

- Common symptoms include a check engine light illuminated on the dashboard, decreased fuel efficiency, rough idling, and potential loss of power.

2. What does the HO2S12 Circuit High Voltage mean in relation to the P0138 code on a 2008 Nissan Altima Sedan?

- This indicates that the oxygen sensor (O2 sensor) located after the catalytic converter is detecting a higher than normal voltage in the circuit.

3. What are the possible causes of the P0138 code on a 2008 Nissan Altima Sedan?

- Potential causes include a faulty oxygen sensor (HO2S12), wiring issues in the oxygen sensor circuit, a vacuum leak, exhaust system leaks, or a malfunctioning catalytic converter.

4. How can I diagnose the P0138 code on my 2008 Nissan Altima Sedan?

- Diagnosis involves using an OBDII scanner to read the code, inspecting the oxygen sensor and its wiring for any damage, checking for exhaust leaks, and testing the functionality of the catalytic converter.

5. Is it safe to continue driving my 2008 Nissan Altima Sedan with the P0138 code present?

- It is not recommended to ignore the P0138 code, as it can lead to further damage to the engine or catalytic converter over time. It is best to address the issue promptly.

6. Can I repair the P0138 code on my 2008 Nissan Altima Sedan myself?

- Depending on your automotive repair skills, you may be able to address the P0138 code yourself by replacing the oxygen sensor, fixing wiring issues, or repairing exhaust leaks. However, professional help may be needed for more complex problems.

7. How much does it typically cost to repair the P0138 code on a 2008 Nissan Altima Sedan?

- The cost of repairing the P0138 code can vary depending on the exact cause of the issue. Simple fixes like replacing the oxygen sensor may cost around $100-$200, while more complex repairs could cost several hundred dollars.

8. Will resetting the check engine light make the P0138 code on my 2008 Nissan Altima Sedan go away?

- Resetting the check engine light may temporarily turn off the light, but it will not fix the underlying issue causing the P0138 code. The problem should be diagnosed and repaired to prevent further issues.

9. How long does it take to repair the P0138 code on a 2008 Nissan Altima Sedan?

- The repair time for the P0138 code can vary depending on the cause of the issue and the complexity of the repair. It can take anywhere from 30 minutes for a simple fix to several hours for more involved repairs.

10. Can the P0138 code on a 2008 Nissan Altima Sedan cause the vehicle to fail emissions testing?

- Yes, the P0138 code typically indicates a problem with the emissions system, which can cause the vehicle to fail emissions testing. It is important to address the issue before undergoing emissions testing.