AutoCodes – Nissan – P0138 2005 Nissan Sentra

P0138 2005 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 2005 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 4,995

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 2005 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 2005 Nissan Sentra - HO2S12 Circuit High Voltage - AutoCodes.com — P0138 2005 Nissan Sentra Code - HO2S12 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P0138 2005 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 2005 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 2005 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 2005 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 2005 Nissan Sentra Code

1. What does the OBDII code P0138 for a 2005 Nissan Sentra mean?

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

2. What are the common symptoms of OBDII code P0138 in a 2005 Nissan Sentra?

- Common symptoms may include poor fuel economy, rough idling, engine hesitation, and an illuminated check engine light.

3. What are the possible causes of the P0138 code in a 2005 Nissan Sentra?

- The most common causes of P0138 include a faulty oxygen sensor, damaged wiring or connectors in the sensor circuit, or an issue with the engine's fuel system.

4. How can I diagnose the P0138 code in my 2005 Nissan Sentra?

- Diagnosing the P0138 code typically involves using an OBDII scanner to retrieve the code, checking the oxygen sensor and its wiring for damage, and testing the sensor's voltage output.

5. Can I still drive my 2005 Nissan Sentra with the P0138 code?

- While it may be possible to drive the vehicle with the P0138 code, it is not recommended as it can lead to decreased fuel efficiency and potential damage to the engine over time.

6. What are some repair tips for fixing the P0138 code in a 2005 Nissan Sentra?

- Repair tips may include replacing the HO2S12 sensor, repairing damaged wiring or connectors, ensuring proper fuel system operation, and clearing the code with an OBDII scanner.

7. How much does it typically cost to repair the P0138 code in a 2005 Nissan Sentra?

- The cost of repairing the P0138 code can vary depending on the exact cause of the issue, but it may range from $100 to $300 for parts and labor.

8. Are there any preventive measures to avoid the P0138 code in a 2005 Nissan Sentra?

- To prevent the P0138 code, it is recommended to perform regular maintenance on the vehicle, including checking and replacing oxygen sensors as needed, and addressing any fuel system issues promptly.

9. Can a DIY enthusiast fix the P0138 code in a 2005 Nissan Sentra?

- Depending on the individual's skill level and access to tools, a DIY enthusiast may be able to replace the oxygen sensor or repair wiring issues causing the P0138 code. However, professional diagnosis is recommended for accurate repair.

10. How urgent is it to address the P0138 code in a 2005 Nissan Sentra?

- While the vehicle may still be operable with the P0138 code, it is important to address the issue promptly to prevent further damage to the engine and ensure optimal fuel efficiency.