AutoCodes – Nissan – P0138 2011 Nissan Altima Sedan

P0138 2011 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 2011 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 4,858

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 2011 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 2011 Nissan Altima Sedan - HO2S12 Circuit High Voltage - AutoCodes.com — P0138 2011 Nissan Altima Sedan Code - HO2S12 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P0138 2011 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 2011 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 2011 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 2011 Nissan Altima Sedan Code

1. What does the OBDII code P0138 for a 2011 Nissan Altima Sedan mean?

The code P0138 on a 2011 Nissan Altima Sedan indicates a high voltage condition in the HO2S12 (Heated Oxygen Sensor Bank 1 Sensor 2) circuit.

2. What are the common symptoms of a HO2S12 Circuit High Voltage issue in a 2011 Nissan Altima Sedan?

Common symptoms of a HO2S12 Circuit High Voltage problem in a 2011 Nissan Altima Sedan may include poor fuel economy, rough idling, engine hesitation, and illuminated Check Engine Light.

3. What are the possible causes of the P0138 code on a 2011 Nissan Altima Sedan?

Potential causes of the P0138 code in a 2011 Nissan Altima Sedan include a faulty oxygen sensor, wiring issues in the HO2S12 circuit, exhaust leaks, or a problem with the engine's fuel system.

4. How can I diagnose a HO2S12 Circuit High Voltage issue in my 2011 Nissan Altima Sedan?

Diagnosing a HO2S12 Circuit High Voltage problem in a 2011 Nissan Altima Sedan involves using an OBDII scanner to retrieve the trouble code, inspecting the oxygen sensor and related wiring, and checking for any exhaust leaks.

5. Can a HO2S12 Circuit High Voltage problem affect the performance of a 2011 Nissan Altima Sedan?

Yes, a HO2S12 Circuit High Voltage issue in a 2011 Nissan Altima Sedan can affect the vehicle's performance by causing poor fuel efficiency, rough running, and potentially damaging the catalytic converter if left unrepaired.

6. How should I repair a P0138 code on my 2011 Nissan Altima Sedan?

Repairing a P0138 code on a 2011 Nissan Altima Sedan typically involves replacing the HO2S12 sensor if it is faulty, addressing any wiring issues, fixing exhaust leaks, and clearing the trouble code with an OBDII scanner.

7. Is it safe to continue driving my 2011 Nissan Altima Sedan with a P0138 code?

It is not recommended to continue driving a 2011 Nissan Altima Sedan with a P0138 code, as it can lead to reduced fuel efficiency, engine performance issues, and potential damage to other components if left unresolved.

8. How much does it cost to fix a HO2S12 Circuit High Voltage problem in a 2011 Nissan Altima Sedan?

The cost of fixing a HO2S12 Circuit High Voltage issue in a 2011 Nissan Altima Sedan can vary depending on the root cause of the problem, but it typically ranges from $100 to $300 for parts and labor.

9. Can a DIY enthusiast repair a P0138 code on a 2011 Nissan Altima Sedan?

While some DIY enthusiasts may be able to address a P0138 code on a 2011 Nissan Altima Sedan by replacing the oxygen sensor or checking for wiring issues, it is recommended to have a professional mechanic diagnose and repair the problem for accurate and safe results.

10. How often does a HO2S12 Circuit High Voltage issue occur in 2011 Nissan Altima Sedans?

HO2S12 Circuit High Voltage problems in 2011 Nissan Altima Sedans are relatively common, especially as the vehicle ages and the oxygen sensor or related components degrade over time. Regular maintenance and timely repairs can help prevent such issues.