AutoCodes – Nissan – P0139 2002 Nissan Sentra

P0139 2002 Nissan Sentra 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 2002 Nissan Sentra 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 3,593

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 Jun 14, 2020

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0139 2002 Nissan Sentra 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 2002 Nissan Sentra - HO2S12 Slow Response - AutoCodes.com — P0139 2002 Nissan Sentra Code - HO2S12 Slow Response

What does this mean?

What are the Possible Causes of the DTC P0139 2002 Nissan Sentra?

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 2002 Nissan Sentra?

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 2002 Nissan Sentra 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 2002 Nissan Sentra Code

1. What does the OBDII code P0139 for a 2002 Nissan Sentra indicate?

- The code P0139 stands for "HO2S12 Slow Response," indicating a slow response from the oxygen sensor located after the catalytic converter in bank 1 sensor 2.

2. What are the common symptoms of a P0139 code in a 2002 Nissan Sentra?

- Common symptoms include decreased fuel efficiency, rough idling, engine misfires, and potential hesitation during acceleration.

3. What are the possible causes of a P0139 code in a 2002 Nissan Sentra?

- The causes may include a faulty oxygen sensor, wiring issues, exhaust leaks, a malfunctioning catalytic converter, or an engine misfire.

4. How can I diagnose the P0139 code in a 2002 Nissan Sentra?

- Diagnosing the P0139 code involves inspecting the oxygen sensor and its wiring, checking for exhaust leaks, testing the catalytic converter, and scanning for any other related codes.

5. How can I repair a P0139 code in a 2002 Nissan Sentra?

- Repair options may include replacing the oxygen sensor, repairing or replacing damaged wiring, fixing any exhaust leaks, addressing engine misfires, or replacing the catalytic converter if necessary.

6. Can a P0139 code in a 2002 Nissan Sentra cause damage if left untreated?

- Ignoring the P0139 code may lead to decreased fuel efficiency, potential damage to the catalytic converter, and continued poor engine performance over time.

7. How long does it typically take to repair a P0139 code in a 2002 Nissan Sentra?

- The repair time for a P0139 code can vary depending on the exact cause and complexity of the issue. It could range from a quick sensor replacement to more extensive repairs involving the exhaust system.

8. Is it safe to continue driving a 2002 Nissan Sentra with a P0139 code?

- While the vehicle may still be operable with a P0139 code, it is recommended to address the issue promptly to prevent potential damage to the engine or catalytic converter.

9. Can a P0139 code in a 2002 Nissan Sentra be triggered by a loose gas cap?

- A loose gas cap is unlikely to trigger a P0139 code specifically, as this code is related to the oxygen sensor's slow response after the catalytic converter.

10. Will resetting the OBDII system clear a P0139 code in a 2002 Nissan Sentra?

- Resetting the OBDII system may temporarily clear the code, but if the underlying issue is not addressed, the code is likely to reappear after driving cycles.