AutoCodes – Nissan – P0138 2009 Nissan Altima Sedan

P0138 2009 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 2009 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 5,753

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 2009 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 2009 Nissan Altima Sedan - HO2S12 Circuit High Voltage - AutoCodes.com — P0138 2009 Nissan Altima Sedan Code - HO2S12 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P0138 2009 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 2009 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 2009 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 2009 Nissan Altima Sedan Code

1. What does the OBDII code P0138 for a 2009 Nissan Altima Sedan mean?

- The code P0138 indicates that the HO2S12 (heated oxygen sensor 2, bank 1 sensor 2) circuit has detected high voltage.

2. What are the common symptoms of the P0138 code in a 2009 Nissan Altima Sedan?

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

3. What are the possible causes of the P0138 code in a 2009 Nissan Altima Sedan?

- The code P0138 can be triggered by a faulty oxygen sensor, wiring issues in the sensor circuit, exhaust leaks, or an engine running rich.

4. How can I diagnose the P0138 code in my 2009 Nissan Altima Sedan?

- Diagnosing the P0138 code typically involves testing the oxygen sensor, inspecting the wiring for damage or corrosion, and checking for exhaust leaks.

5. Can I drive my 2009 Nissan Altima Sedan with the P0138 code?

- It is not recommended to drive your vehicle with the P0138 code present, as it can lead to poor engine performance and potential damage if left unresolved.

6. How do I repair the P0138 code in my 2009 Nissan Altima Sedan?

- Repairing the P0138 code may involve replacing the HO2S12 sensor, repairing damaged wiring, fixing exhaust leaks, or addressing any issues causing the engine to run rich.

7. Is it possible to reset the P0138 code in a 2009 Nissan Altima Sedan without fixing the underlying issue?

- While you can clear the code with an OBDII scanner, it is crucial to address the root cause of the problem to prevent further issues and ensure proper vehicle operation.

8. How much does it cost to repair the P0138 code in a 2009 Nissan Altima Sedan?

- The cost of repairing the P0138 code can vary depending on the specific issue, but it may range from $100 to $300 for parts and labor.

9. Can a DIY enthusiast fix the P0138 code in a 2009 Nissan Altima Sedan?

- Depending on your skill level and access to tools, DIY enthusiasts may be able to address the P0138 code by replacing the oxygen sensor or repairing wiring issues.

10. How often does the P0138 code occur in a 2009 Nissan Altima Sedan?

- The P0138 code can occur sporadically or persistently, and its frequency may vary depending on the vehicle's condition and maintenance history.