AutoCodes – Infiniti – P0138 2003 Infiniti G35

P0138 2003 Infiniti G35 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 2003 Infiniti G35 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 4,633

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 Apr 01, 2024

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0138 2003 Infiniti G35 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 2003 Infiniti G35 - HO2S12 Circuit High Voltage - AutoCodes.com — P0138 2003 Infiniti G35 Code - HO2S12 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P0138 2003 Infiniti G35?

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 2003 Infiniti G35?

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 2003 Infiniti G35 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 2003 Infiniti G35 Code

1. What does OBDII code P0138 for a 2003 Infiniti G35 mean?

Code P0138 indicates a high voltage condition in the HO2S12 (Heated Oxygen Sensor Bank 1 Sensor 2) circuit of the vehicle.

2. What are the common symptoms of OBDII code P0138 in a 2003 Infiniti G35?

Common symptoms include poor fuel economy, rough idling, engine misfires, and the illumination of the check engine light.

3. What are the possible causes of OBDII code P0138 in a 2003 Infiniti G35?

Potential causes include a faulty HO2S12 sensor, wiring issues in the sensor circuit, exhaust leaks, or problems with the engine's fuel system.

4. How can I diagnose the OBDII code P0138 in my 2003 Infiniti G35?

Diagnosis typically involves using an OBDII scanner to retrieve the code, inspecting the HO2S12 sensor and its wiring for damage, and checking for exhaust leaks.

5. Can I still drive my 2003 Infiniti G35 with OBDII code P0138?

It is not recommended to continue driving with code P0138 as it can lead to poor engine performance and potential damage in the long run. It's best to address the issue promptly.

6. How can I repair OBDII code P0138 in my 2003 Infiniti G35?

Repair options may include replacing the HO2S12 sensor, repairing damaged wiring, fixing exhaust leaks, or addressing any fuel system issues that may be contributing to the code.

7. Can I reset the OBDII code P0138 in my 2003 Infiniti G35 without fixing the underlying issue?

While you can clear the code using an OBDII scanner, the check engine light is likely to reappear if the root cause of the code is not addressed.

8. Is it possible for a dirty or contaminated sensor to trigger OBDII code P0138 in a 2003 Infiniti G35?

Yes, a dirty or contaminated HO2S12 sensor can sometimes cause erroneous readings and lead to a high voltage condition, triggering code P0138.

9. How much does it typically cost to repair OBDII code P0138 in a 2003 Infiniti G35?

The cost of repair can vary depending on the specific issue causing the code, but it may range from around $100 to $300 or more, including parts and labor.

10. How often should I replace the oxygen sensors in my 2003 Infiniti G35 to prevent OBDII code P0138 from recurring?

Oxygen sensors typically have a lifespan of around 60,000 to 90,000 miles. Regularly inspecting and replacing sensors as needed can help prevent issues like code P0138 from reoccurring.