AutoCodes – Audi – P0139 Audi

P0139 Audi Code - HO2S12 Sensor Circuit 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 Audi indicates HO2S12 Sensor Circuit 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 13,395

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 12, 2019

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0139 Audi 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 Audi - HO2S12 Sensor Circuit Slow Response - AutoCodes.com — P0139 Audi Code - HO2S12 Sensor Circuit Slow Response

What does this mean?

What are the Possible Causes of the DTC P0139 Audi?

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 Audi?

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 Audi 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 Audi Code

1. What are the common symptoms of OBDII code P0139 in an Audi?

- Common symptoms include poor fuel efficiency, rough idling, and hesitation during acceleration.

2. What does the OBDII code P0139 in an Audi indicate?

- The code P0139 indicates a slow response from the HO2S12 sensor circuit, which is the downstream oxygen sensor in bank 1.

3. What are the possible causes of the HO2S12 sensor circuit slow response in an Audi?

- Possible causes include a faulty oxygen sensor, wiring issues, exhaust leaks, or a problem with the engine control module.

4. How can I diagnose the HO2S12 sensor circuit slow response in my Audi?

- You can diagnose this issue by performing a visual inspection of the oxygen sensor and its wiring, conducting a voltage test, and using a scan tool to monitor sensor data.

5. Can I continue driving my Audi with the OBDII code P0139 present?

- It is not recommended to drive your Audi with the code P0139 present, as it can lead to further damage to the engine and affect overall performance.

6. How can I repair the HO2S12 sensor circuit slow response in my Audi?

- Repair options may include replacing the oxygen sensor, repairing any damaged wiring, fixing exhaust leaks, or reprogramming the engine control module.

7. Is it possible to clear the OBDII code P0139 in an Audi without fixing the underlying issue?

- Clearing the code without addressing the underlying problem will only temporarily turn off the check engine light, but the issue will persist and the code may reappear.

8. How long does it typically take to repair the HO2S12 sensor circuit slow response in an Audi?

- The repair time can vary depending on the exact cause of the issue, but it may take anywhere from 1 to 3 hours to diagnose and fix the problem.

9. Can a DIY enthusiast repair the HO2S12 sensor circuit slow response in an Audi?

- While some aspects of the repair can be done by a skilled DIY enthusiast, it is recommended to consult a professional mechanic for proper diagnosis and repair to ensure the issue is fully resolved.

10. Will fixing the HO2S12 sensor circuit slow response improve the overall performance of my Audi?

- Yes, fixing this issue can help improve fuel efficiency, engine performance, and reduce harmful emissions, leading to a smoother driving experience.