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P0139 Jeep Code - O2 sensor 1/2 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 Jeep indicates O2 sensor 1/2 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 41,852
How popular is this code, among other codes? Medium
What is this?
Table of contents Created and updated by William Orellana on Apr 12, 2019
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Code P0139 Jeep 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 Jeep - O2 sensor 1/2 Slow response - AutoCodes.com
P0139 Jeep Code - O2 sensor 1/2 Slow response
What does this mean?

What are the Possible Causes of the DTC P0139 Jeep?

  • 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 Jeep?

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 Jeep 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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Need more information on how to fix the P0139 Jeep code? Get Access to Factory Service Manuals

Need Help with the Code?

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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 Jeep Code

1. What does the OBDII code P0139 mean on a Jeep?

P0139 indicates that the oxygen sensor located downstream of the catalytic converter (sensor 1/2) is responding more slowly than expected to changes in exhaust gas oxygen levels.

2. What are the common symptoms of the P0139 code on a Jeep?

Symptoms may include an illuminated check engine light, reduced fuel efficiency, poor engine performance, or a noticeable sulfur-like odor from the exhaust.

3. What causes the P0139 code on a Jeep?

Common causes include a failing downstream oxygen sensor, exhaust leaks, a clogged catalytic converter, wiring or connector issues, or engine performance problems like a rich or lean air-fuel mixture.

4. Can a dirty or faulty oxygen sensor trigger the P0139 code?

Yes, a dirty or failing oxygen sensor can result in a slow response time, triggering the P0139 code.

5. How do you diagnose the P0139 code on a Jeep?

Diagnosis involves using a scan tool to monitor the oxygen sensor's response time, inspecting sensor wiring and connectors, checking for exhaust leaks, and testing the air-fuel mixture.

6. How serious is the P0139 code on a Jeep?

While it may not immediately affect drivability, ignoring the P0139 code can lead to reduced fuel efficiency, increased emissions, and potential damage to the catalytic converter.

7. Can a vacuum or exhaust leak cause the P0139 code?

Yes, vacuum or exhaust leaks can disrupt oxygen sensor readings, leading to the P0139 code.

8. How do you fix the P0139 code on a Jeep?

Repairs may include replacing the oxygen sensor, repairing wiring or connectors, fixing exhaust leaks, or addressing issues with the air-fuel mixture or catalytic converter.

9. Can I drive my Jeep with the P0139 code?

You can drive with the P0139 code temporarily, but it’s best to address the issue promptly to avoid long-term damage or decreased fuel efficiency.

10. How much does it cost to fix the P0139 code on a Jeep?

Repair costs vary but typically range from $150 to $300 for oxygen sensor replacement, depending on labor rates and the cost of parts.

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