AutoCodes – Nissan – P0138 2002 Nissan Sentra

P0138 2002 Nissan Sentra 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 Sentra 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 5,690

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

What does this mean?

What are the Possible Causes of the DTC P0138 2002 Nissan Sentra?

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 Sentra?

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 Sentra 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.

Need more information about the P0138 2002 Nissan Sentra code?

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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 Sentra Code

1. What are common symptoms of OBDII code P0138 on a 2002 Nissan Sentra?

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

2. What does the HO2S12 Circuit High Voltage code P0138 mean for a 2002 Nissan Sentra?

- This code indicates that the oxygen sensor (O2 sensor) located in bank 1 sensor 2 is detecting a high voltage condition.

3. What are possible causes of OBDII code P0138 on a 2002 Nissan Sentra?

- Possible causes include a faulty oxygen sensor, wiring issues in the sensor circuit, a vacuum leak, exhaust system leaks, or engine misfires.

4. How can I diagnose the HO2S12 Circuit High Voltage code P0138 on my 2002 Nissan Sentra?

- Diagnosis typically involves using an OBDII scanner to read the code, checking the oxygen sensor's voltage readings, inspecting the sensor wiring, and looking for any exhaust or vacuum leaks.

5. Can I continue driving my 2002 Nissan Sentra with OBDII code P0138?

- It is not advisable to drive for an extended period with this code as it can lead to poor engine performance and potential damage to the catalytic converter.

6. How do I repair OBDII code P0138 on my 2002 Nissan Sentra?

- Repair options may include replacing the oxygen sensor, repairing any damaged wiring, fixing vacuum or exhaust leaks, and ensuring proper engine operation.

7. Will resetting the Check Engine Light fix the P0138 code on my 2002 Nissan Sentra?

- Resetting the light may temporarily turn it off, but it will not fix the underlying issue causing the code. Proper diagnosis and repair are recommended.

8. How much does it cost to repair OBDII code P0138 on a 2002 Nissan Sentra?

- The cost of repair can vary depending on the exact cause of the code, but it may involve parts and labor expenses ranging from $100 to $500 or more.

9. Can a DIY enthusiast fix OBDII code P0138 on a 2002 Nissan Sentra?

- Depending on the individual's skill level and access to tools, some DIY enthusiasts may be able to diagnose and repair this code, especially if it involves simple tasks like sensor replacement.

10. How often does the HO2S12 Circuit High Voltage code P0138 occur in 2002 Nissan Sentras?

- While the occurrence rate may vary, this code is relatively common in older vehicles like the 2002 Nissan Sentra due to sensor wear and wiring degradation over time.