AutoCodes – Nissan – P0138 2012 Nissan Sentra

P0138 2012 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 2012 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 3,923

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 2012 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 2012 Nissan Sentra - HO2S12 Circuit High Voltage - AutoCodes.com — P0138 2012 Nissan Sentra Code - HO2S12 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P0138 2012 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 2012 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 2012 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 2012 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 2012 Nissan Sentra Code

1. What does OBDII code P0138 on a 2012 Nissan Sentra mean?

The OBDII code P0138 for a 2012 Nissan Sentra indicates a fault with the HO2S12 (Heated Oxygen Sensor Bank 1 Sensor 2) circuit, specifically high voltage.

2. What are the common symptoms of OBDII code P0138 on a 2012 Nissan Sentra?

Common symptoms of OBDII code P0138 on a 2012 Nissan Sentra may include poor fuel economy, rough idling, engine hesitation, or the illumination of the check engine light.

3. What are the possible causes of OBDII code P0138 on a 2012 Nissan Sentra?

Possible causes of OBDII code P0138 on a 2012 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 HO2S12 circuit high voltage issue in a 2012 Nissan Sentra?

To diagnose the HO2S12 circuit high voltage issue in a 2012 Nissan Sentra, you can use a scan tool to read the code, visually inspect the sensor and its wiring for any damage, and perform voltage tests to determine if the sensor is functioning correctly.

5. Is it safe to continue driving a 2012 Nissan Sentra with OBDII code P0138?

It is not recommended to continue driving a 2012 Nissan Sentra with OBDII code P0138, as it can lead to decreased fuel efficiency and potential damage to the catalytic converter.

6. Can I repair OBDII code P0138 on a 2012 Nissan Sentra myself?

Depending on your mechanical skills, you may be able to repair OBDII code P0138 on a 2012 Nissan Sentra yourself by replacing the faulty HO2S12 sensor, fixing any wiring issues, or addressing exhaust leaks. However, professional diagnosis and repair may be necessary for complex cases.

7. How much does it cost to fix OBDII code P0138 on a 2012 Nissan Sentra?

The cost to fix OBDII code P0138 on a 2012 Nissan Sentra can vary depending on the underlying issue. Replacing a faulty HO2S12 sensor may range from $100 to $300, while addressing wiring or ECM problems can increase the repair cost.

8. Can a bad HO2S12 sensor cause other issues in a 2012 Nissan Sentra?

Yes, a bad HO2S12 sensor can cause other issues in a 2012 Nissan Sentra, such as poor engine performance, increased emissions, and potential damage to the catalytic converter if left unresolved.

9. How often should the HO2S12 sensor be replaced in a 2012 Nissan Sentra?

The HO2S12 sensor in a 2012 Nissan Sentra typically lasts around 100,000 miles, but it is recommended to follow the manufacturer's maintenance schedule and replace it if any issues or codes like P0138 arise.

10. Is OBDII code P0138 a common issue in 2012 Nissan Sentras?

OBDII code P0138, indicating HO2S12 circuit high voltage, is a relatively common issue in 2012 Nissan Sentras, especially as the vehicle ages and the sensor or related components wear out. Regular maintenance and timely repairs can help prevent this code from recurring.