AutoCodes – Infiniti – P0139 2005 Infiniti G35

P0139 2005 Infiniti G35 Code - HO2S12 Slow Response

Quick Answer

The Heated Oxygen Sensor 2 (HO2S), 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: P0139 2005 Infiniti G35 indicates HO2S12 Slow Response.
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 2,764

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 P0139 2005 Infiniti G35 Description

The Heated Oxygen Sensor 2 (HO2S), 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 P0139 2005 Infiniti G35 - HO2S12 Slow Response - AutoCodes.com — P0139 2005 Infiniti G35 Code - HO2S12 Slow Response

What does this mean?

What are the Possible Causes of the DTC P0139 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
Inappropriate fuel pressure
Faulty fuel injectors
Intake air leaks may be faulty
Exhaust gas leaks

How to Fix the DTC P0139 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 P0139 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 P0139 2005 Infiniti G35 Code

1. What are the common symptoms of OBDII code P0139 in a 2005 Infiniti G35?

The common symptoms include poor fuel economy, rough idling, hesitation during acceleration, and the illumination of the check engine light.

2. What does the OBDII code P0139 for a 2005 Infiniti G35 indicate?

The code P0139 indicates a slow response from the downstream oxygen sensor (HO2S12) located after the catalytic converter.

3. What are the possible causes of the HO2S12 slow response code in a 2005 Infiniti G35?

Common causes include a faulty oxygen sensor, wiring issues, exhaust leaks, engine misfires, or a malfunctioning catalytic converter.

4. How can I diagnose the cause of the P0139 code in my 2005 Infiniti G35?

You can diagnose the issue by conducting a visual inspection of the oxygen sensor and its wiring, checking for exhaust leaks, performing a fuel system test, and using a scan tool to monitor sensor data.

5. Can I drive my 2005 Infiniti G35 with the P0139 code?

It is not recommended to drive your vehicle with the P0139 code as it can lead to poor engine performance, increased emissions, and potential damage to the catalytic converter.

6. How can I repair the HO2S12 slow response code 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 replacing the catalytic converter if necessary.

7. Is it safe to clear the P0139 code in my 2005 Infiniti G35 without fixing the issue?

Clearing the code without addressing the underlying problem is not recommended as the issue may persist, leading to further engine problems and potential failure of emissions tests.

8. How much does it typically cost to repair the P0139 code in a 2005 Infiniti G35?

The cost of repair can vary depending on the exact cause of the code, but it may range from $100 to $500 or more, including parts and labor.

9. Can a DIY enthusiast fix the P0139 code in a 2005 Infiniti G35?

Depending on your skill level and access to tools, you may be able to replace the oxygen sensor or address minor wiring issues yourself. However, more complex repairs may require professional assistance.

10. Will the P0139 code in my 2005 Infiniti G35 reset on its own?

The code may clear itself after a certain number of drive cycles if the issue is resolved. However, it is recommended to diagnose and repair the underlying problem to prevent the code from reoccurring.