AutoCodes – Nissan – P0138 2003 Nissan Altima Sedan

P0138 2003 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 2003 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 10,057

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 2003 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 2003 Nissan Altima Sedan - HO2S12 Circuit High Voltage - AutoCodes.com — P0138 2003 Nissan Altima Sedan Code - HO2S12 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P0138 2003 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 2003 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 2003 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 2003 Nissan Altima Sedan Code

1. What are the common symptoms of OBDII code P0138 on a 2003 Nissan Altima Sedan?

- Common symptoms include poor fuel economy, rough idling, hesitation during acceleration, and the illumination of the Check Engine light.

2. What does the OBDII code P0138 "HO2S12 Circuit High Voltage" indicate in a 2003 Nissan Altima Sedan?

- This code indicates that the oxygen sensor (HO2S12) located after the catalytic converter is detecting a high voltage condition.

3. What are the possible causes of OBDII code P0138 on a 2003 Nissan Altima Sedan?

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

4. How can I diagnose the cause of OBDII code P0138 on my 2003 Nissan Altima Sedan?

- To diagnose the issue, you can use an OBDII scanner to read the code, visually inspect the oxygen sensor and its wiring, check for exhaust leaks, and perform voltage tests on the sensor.

5. Can I drive my 2003 Nissan Altima Sedan with OBDII code P0138?

- It is not recommended to drive the vehicle with a P0138 code for an extended period as it can lead to decreased fuel efficiency and potentially cause damage to the catalytic converter.

6. How can I repair OBDII code P0138 on a 2003 Nissan Altima Sedan?

- Repair options include replacing the oxygen sensor (HO2S12), repairing any damaged wiring in the sensor circuit, fixing exhaust leaks, and addressing any other underlying issues causing the high voltage condition.

7. Will resetting the Check Engine light resolve OBDII code P0138 on my 2003 Nissan Altima Sedan?

- Simply resetting the Check Engine light will not fix the underlying issue causing the P0138 code. It is important to diagnose and repair the root cause of the problem.

8. How much does it cost to repair OBDII code P0138 on a 2003 Nissan Altima Sedan?

- The cost of repairing P0138 can vary depending on the specific cause of the issue, but it may involve replacing the oxygen sensor, which can range from $100 to $300 including parts and labor.

9. Can a DIY enthusiast fix OBDII code P0138 on a 2003 Nissan Altima Sedan?

- Depending on the DIY enthusiast's skill level, it is possible to address some of the common causes of P0138, such as replacing the oxygen sensor or repairing simple wiring issues. However, more complex problems may require professional assistance.

10. How often does OBDII code P0138 occur in a 2003 Nissan Altima Sedan?

- The occurrence of P0138 can vary, but it is a relatively common code related to oxygen sensor malfunctions in vehicles, including the 2003 Nissan Altima Sedan.