AutoCodes – Nissan – P0138 2002 Nissan Altima Sedan

P0138 2002 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 2002 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 9,158

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 2002 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 2002 Nissan Altima Sedan - HO2S12 Circuit High Voltage - AutoCodes.com — P0138 2002 Nissan Altima Sedan Code - HO2S12 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P0138 2002 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 2002 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 2002 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 2002 Nissan Altima Sedan Code

1. What are the common symptoms of OBDII code P0138 on a 2002 Nissan Altima Sedan?

- Common symptoms include poor fuel economy, rough idling, lack of power, and the illumination of the Check Engine Light.

2. What does the OBDII code P0138 for a 2002 Nissan Altima Sedan indicate?

- The code P0138 indicates that the HO2S12 (Heated Oxygen Sensor 2 Bank 1 Sensor 2) circuit is registering a high voltage condition.

3. What are some possible causes of the HO2S12 Circuit High Voltage code on a 2002 Nissan Altima Sedan?

- Potential causes include a faulty oxygen sensor, wiring issues, exhaust leaks, engine misfires, or a malfunctioning engine control module (ECM).

4. How can I diagnose the issue causing the P0138 code on my 2002 Nissan Altima Sedan?

- A thorough diagnostic process involves checking the oxygen sensor's wiring, inspecting for exhaust leaks, testing the sensor's voltage, and scanning for any other related trouble codes.

5. Can a dirty or contaminated oxygen sensor cause the P0138 code on a 2002 Nissan Altima Sedan?

- Yes, a dirty or contaminated oxygen sensor can lead to incorrect readings and trigger the P0138 code. It is essential to ensure the sensor is clean and functioning properly.

6. What repairs are typically needed to address the HO2S12 Circuit High Voltage code in a 2002 Nissan Altima Sedan?

- Repairs may involve replacing the oxygen sensor, repairing damaged wiring, fixing exhaust leaks, addressing engine misfires, or reprogramming the ECM if necessary.

7. Is it safe to continue driving my 2002 Nissan Altima Sedan with the P0138 trouble code?

- It is generally not recommended to drive with the P0138 code illuminated, as it can lead to reduced fuel efficiency and potentially cause damage to the catalytic converter over time.

8. How much does it cost to fix the HO2S12 Circuit High Voltage issue on a 2002 Nissan Altima Sedan?

- The cost of repairs can vary depending on the exact cause of the problem. Replacing the oxygen sensor or repairing wiring issues may cost a few hundred dollars at a professional repair shop.

9. Can I reset the Check Engine Light after fixing the P0138 code on my 2002 Nissan Altima Sedan?

- Yes, once the underlying issue causing the P0138 code is fixed, the Check Engine Light can be reset using an OBDII scanner to clear the code and turn off the warning light.

10. Will the OBDII code P0138 on a 2002 Nissan Altima Sedan affect the vehicle's emissions and overall performance?

- Yes, unresolved issues related to the P0138 code can impact emissions levels, fuel efficiency, and engine performance, making it important to address the problem promptly.