AutoCodes – Jeep – P0138 Jeep

P0138 Jeep Code - O2 Sensor 1/2 Circuit High

Quick Answer

The Heated Oxygen Sensor 2 (HO2S) (Rear O2 Sensor), 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: P0138 Jeep indicates O2 Sensor 1/2 Circuit High.
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 78,074

How popular is this code, among other codes? Medium

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 May 27, 2022

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes ▶
Cost to Diagnose
FAQs
Comments
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Code P0138 Jeep Description

The Heated Oxygen Sensor 2 (HO2S) (Rear O2 Sensor), 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 P0138 Jeep - O2 Sensor 1/2 Circuit High - AutoCodes.com — P0138 Jeep Code - O2 Sensor 1/2 Circuit High

What does this mean?

What are the Possible Causes of the DTC P0138 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
Intake air leaks
Exhaust gas leaks
Inappropriate fuel pressure
Faulty fuel injectors

How to Fix the DTC P0138 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.

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What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0138 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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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 P0138 Jeep Code

1. What does OBDII code P0138 for a Jeep mean?

The OBDII code P0138 for a Jeep indicates a problem with the O2 Sensor 1/2 Circuit High voltage.

2. What are the common symptoms of OBDII code P0138 in a Jeep?

Common symptoms of OBDII code P0138 in a Jeep include poor fuel economy, engine misfires, rough idling, and the illumination of the Check Engine Light.

3. What are the possible causes of O2 Sensor 1/2 Circuit High in a Jeep?

Possible causes of O2 Sensor 1/2 Circuit High in a Jeep include a faulty oxygen sensor, wiring issues, exhaust leaks, or a problem with the engine's fuel system.

4. How can I diagnose the OBDII code P0138 in my Jeep?

To diagnose OBDII code P0138 in your Jeep, you can use an OBDII scanner to retrieve the code, visually inspect the oxygen sensor and related wiring, and perform voltage tests to pinpoint the issue.

5. Can I drive my Jeep with the OBDII code P0138?

It is not recommended to drive your Jeep with the OBDII code P0138 as it can lead to poor engine performance and potentially cause further damage to the vehicle.

6. How do I repair O2 Sensor 1/2 Circuit High in my Jeep?

To repair O2 Sensor 1/2 Circuit High in your Jeep, you may need to replace the faulty oxygen sensor, repair any damaged wiring, fix exhaust leaks, or address issues with the fuel system.

7. How much does it cost to fix OBDII code P0138 in a Jeep?

The cost to fix OBDII code P0138 in a Jeep can vary depending on the root cause of the issue, but it may range from $100 to $300 for parts and labor.

8. Can a DIY enthusiast fix O2 Sensor 1/2 Circuit High in a Jeep?

If you have the necessary tools and knowledge, you may be able to fix O2 Sensor 1/2 Circuit High in your Jeep as a DIY project. However, it is recommended to consult a professional if you are unsure.

9. Will resetting the Check Engine Light resolve OBDII code P0138 in my Jeep?

Simply resetting the Check Engine Light will not fix OBDII code P0138 in your Jeep. It is essential to diagnose the underlying issue and make the necessary repairs to resolve the problem.

10. How often should I check the oxygen sensors in my Jeep to prevent O2 Sensor 1/2 Circuit High issues?

It is recommended to check the oxygen sensors in your Jeep during routine maintenance or whenever you experience symptoms of a malfunction, such as poor fuel economy or engine performance issues.