AutoCodes – Infiniti – P0138 2005 Infiniti G35

P0138 2005 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 2005 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 3,681

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 2005 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 2005 Infiniti G35 - HO2S12 Circuit High Voltage - AutoCodes.com — P0138 2005 Infiniti G35 Code - HO2S12 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P0138 2005 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 2005 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 2005 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 2005 Infiniti G35 Code

1. What are the common symptoms of OBDII code P0138 in a 2005 Infiniti G35?

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

2. What does the OBDII code P0138 ("HO2S12 Circuit High Voltage") on a 2005 Infiniti G35 mean?

- This code indicates that the downstream oxygen sensor (HO2S12) in bank 1 is detecting a voltage that is higher than normal.

3. What are the possible causes of OBDII code P0138 in a 2005 Infiniti G35?

- Potential causes include a faulty oxygen sensor, wiring issues, exhaust leaks, engine misfires, or a problem with the engine control module (ECM).

4. How can I diagnose the OBDII code P0138 in my 2005 Infiniti G35?

- Diagnosis typically involves checking the oxygen sensor's wiring and connections, inspecting for exhaust leaks, and performing tests to identify any underlying issues.

5. Can I continue driving my 2005 Infiniti G35 with OBDII code P0138?

- While the vehicle may still be operational, it is recommended to address the issue promptly to prevent potential damage to the catalytic converter and ensure optimal engine performance.

6. How can I repair OBDII code P0138 in my 2005 Infiniti G35?

- Repair options may include replacing the downstream oxygen sensor, repairing any damaged wiring, fixing exhaust leaks, addressing engine misfires, or reprogramming the ECM.

7. Should I reset the check engine light after fixing OBDII code P0138 in my 2005 Infiniti G35?

- Yes, it is advisable to clear the trouble codes and reset the check engine light using an OBDII scanner after resolving the underlying issue.

8. How much does it cost to fix OBDII code P0138 in a 2005 Infiniti G35?

- The cost of repairs can vary depending on the root cause of the issue, but it may range from a few hundred to over a thousand dollars, including parts and labor.

9. How often does OBDII code P0138 occur in 2005 Infiniti G35 vehicles?

- While not extremely common, OBDII code P0138 can occur in 2005 Infiniti G35 models due to various factors like sensor wear, wiring issues, or exhaust system problems.

10. Can a DIY enthusiast fix OBDII code P0138 in a 2005 Infiniti G35?

- Depending on the individual's skill level and access to tools, some DIY enthusiasts may be able to address simpler causes of P0138, such as replacing the oxygen sensor or checking for loose connections. However, more complex issues may require professional assistance.