AutoCodes – Infiniti – P0139 2003 Infiniti G35

P0139 2003 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 2003 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 3,766

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 2003 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 2003 Infiniti G35 - HO2S12 Slow Response - AutoCodes.com — P0139 2003 Infiniti G35 Code - HO2S12 Slow Response

What does this mean?

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

How to Fix the DTC P0139 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 P0139 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 P0139 2003 Infiniti G35 Code

What does the OBDII code P0139 mean on a 2003 Infiniti G35?

The P0139 code indicates that the Oxygen Sensor (HO2S) located in bank 1, sensor 2, has a slower than normal response time. This sensor is typically found in the exhaust system after the catalytic converter.

What are the common symptoms of code P0139 in a 2003 Infiniti G35?

Symptoms may include a check engine light, decreased fuel efficiency, a rough idle, or a noticeable drop in engine performance.

What can cause the P0139 code to appear in a 2003 Infiniti G35?

Common causes include a faulty oxygen sensor, exhaust leaks near the sensor, damaged or corroded wiring, or problems with the catalytic converter.

How do I fix the P0139 code in a 2003 Infiniti G35?

To fix the P0139 code, start by inspecting the oxygen sensor and its wiring for damage or corrosion. Replace the oxygen sensor if it appears faulty. Also, check for and repair any exhaust leaks.

Is it safe to drive my 2003 Infiniti G35 with a P0139 code?

While you can drive with a P0139 code, it's advisable to address the issue promptly as ignoring it could lead to reduced fuel efficiency, potential damage to the catalytic converter, or other engine problems.

How can I prevent the P0139 code from occurring in my 2003 Infiniti G35?

Regular maintenance is key. Ensure timely servicing of the vehicleâ€™s exhaust system, keep the oxygen sensors clean, and address any engine or exhaust issues promptly to prevent this code from occurring.

What tools are needed to diagnose the P0139 code on a 2003 Infiniti G35?

A diagnostic scan tool is essential to read the fault code. Additionally, a digital multimeter and an oscilloscope can help further investigate the oxygen sensor's performance and check for wiring issues.

How much does it typically cost to repair the P0139 code in a 2003 Infiniti G35?

The cost can vary widely depending on the specific repair needed. Replacing an oxygen sensor can cost anywhere from $200 to $400 including parts and labor. Additional repairs such as fixing exhaust leaks or replacing wiring might increase the cost.

Can a faulty catalytic converter cause the P0139 code in a 2003 Infiniti G35?

Yes, a failing catalytic converter can lead to a P0139 code. If the converter is not processing exhaust gases efficiently, it can affect the readings and performance of the oxygen sensors.