AutoCodes – Nissan – P0138 2008 Nissan Sentra

P0138 2008 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 2008 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 4,033

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 2008 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 2008 Nissan Sentra - HO2S12 Circuit High Voltage - AutoCodes.com — P0138 2008 Nissan Sentra Code - HO2S12 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P0138 2008 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 2008 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 2008 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 2008 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 2008 Nissan Sentra Code

1. What does the OBDII code P0138 mean for a 2008 Nissan Sentra?

The code P0138 for a 2008 Nissan Sentra indicates a high voltage condition in the HO2S12 (Heated Oxygen Sensor Bank 1 Sensor 2) circuit.

2. What are common symptoms of OBDII code P0138 in a 2008 Nissan Sentra?

Common symptoms of code P0138 in a 2008 Nissan Sentra may include poor fuel economy, rough idling, engine hesitation, and the illumination of the check engine light.

3. What are possible causes of OBDII code P0138 in a 2008 Nissan Sentra?

Possible causes of code P0138 in a 2008 Nissan Sentra include a faulty HO2S12 sensor, wiring issues in the sensor circuit, exhaust leaks, or a malfunctioning engine control module (ECM).

4. How can I diagnose the OBDII code P0138 in my 2008 Nissan Sentra?

To diagnose code P0138 in a 2008 Nissan Sentra, you can perform a visual inspection of the sensor and its wiring, test the sensor's voltage output, check for exhaust leaks, and use a scan tool to monitor sensor data.

5. What is the recommended repair for OBDII code P0138 in a 2008 Nissan Sentra?

The recommended repair for code P0138 in a 2008 Nissan Sentra may involve replacing the HO2S12 sensor, repairing any damaged wiring, fixing exhaust leaks, or reprogramming the ECM if necessary.

6. Can I drive my 2008 Nissan Sentra with OBDII code P0138?

It is not recommended to drive a 2008 Nissan Sentra with OBDII code P0138 for an extended period as it can affect the vehicle's performance and fuel efficiency. It's best to address the issue promptly.

7. How much does it typically cost to fix OBDII code P0138 in a 2008 Nissan Sentra?

The cost to fix OBDII code P0138 in a 2008 Nissan Sentra can vary depending on the root cause of the issue. Replacing the HO2S12 sensor may cost between $100 to $200, while addressing wiring or ECM problems can be more expensive.

8. Can a DIY enthusiast repair OBDII code P0138 in a 2008 Nissan Sentra?

DIY enthusiasts with the necessary tools and knowledge of automotive repair may be able to address OBDII code P0138 in a 2008 Nissan Sentra. However, it's important to diagnose the issue accurately before attempting any repairs.

9. How soon should I address OBDII code P0138 in my 2008 Nissan Sentra?

It is recommended to address OBDII code P0138 in a 2008 Nissan Sentra as soon as possible to prevent potential damage to the vehicle's engine and emission control system, as well as to ensure optimal performance.

10. Will resetting the OBDII code P0138 in my 2008 Nissan Sentra make it go away permanently?

Resetting the OBDII code P0138 in a 2008 Nissan Sentra may temporarily turn off the check engine light, but if the underlying issue is not resolved, the code is likely to reappear. It's essential to diagnose and fix the root cause of the problem.