AutoCodes – Nissan – P0139 2004 Nissan Sentra

P0139 2004 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 2004 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 3,925

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 2004 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 2004 Nissan Sentra - HO2S12 Slow Response - AutoCodes.com — P0139 2004 Nissan Sentra Code - HO2S12 Slow Response

What does this mean?

What are the Possible Causes of the DTC P0139 2004 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 2004 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 2004 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 2004 Nissan Sentra Code

1. What does the OBDII code P0139 for a 2004 Nissan Sentra indicate?

The code P0139 for a 2004 Nissan Sentra indicates a slow response from the downstream oxygen sensor (HO2S12).

2. What are the common symptoms of P0139 in a 2004 Nissan Sentra?

Common symptoms of P0139 in a 2004 Nissan Sentra may include reduced fuel efficiency, rough idling, and hesitation during acceleration.

3. What are the possible causes of the P0139 code in a 2004 Nissan Sentra?

Possible causes of the P0139 code in a 2004 Nissan Sentra include a faulty oxygen sensor, wiring issues, exhaust system leaks, or a malfunctioning catalytic converter.

4. How can I diagnose the P0139 code in a 2004 Nissan Sentra?

To diagnose the P0139 code in a 2004 Nissan Sentra, you can use an OBDII scanner to read the code and then inspect the oxygen sensor, wiring connections, and exhaust system for any visible issues.

5. Can I continue driving my 2004 Nissan Sentra with the P0139 code?

It is not recommended to continue driving your 2004 Nissan Sentra with the P0139 code as it can lead to further damage to the engine and emission control system.

6. What is the repair process for fixing the P0139 code in a 2004 Nissan Sentra?

The repair process for fixing the P0139 code in a 2004 Nissan Sentra typically involves replacing the downstream oxygen sensor (HO2S12) and addressing any underlying issues such as wiring problems or exhaust leaks.

7. How much does it cost to repair the P0139 code in a 2004 Nissan Sentra?

The cost to repair the P0139 code in a 2004 Nissan Sentra can vary depending on the labor rates and parts needed, but it is generally recommended to budget for a few hundred dollars for parts and labor.

8. Can I reset the P0139 code in a 2004 Nissan Sentra without fixing the underlying issue?

While you can clear the P0139 code using an OBDII scanner, it is not recommended to do so without fixing the underlying issue as the problem may persist and potentially cause more damage over time.

9. How often does the P0139 code occur in a 2004 Nissan Sentra?

The occurrence of the P0139 code in a 2004 Nissan Sentra can vary depending on the vehicle's maintenance history, driving conditions, and overall health of the emission control system.

10. Is the P0139 code a common issue in 2004 Nissan Sentras?

The P0139 code can be a relatively common issue in 2004 Nissan Sentras, especially in older vehicles with high mileage or poor maintenance records. Regular inspections and maintenance can help prevent this code from appearing.