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Engine-Codes – Mercury – U0138 Mercury

U0138 Mercury Code - Lost Communication With All Terrain Control Module

Quick Answer

The U0138 diagnostic trouble code (DTC) for Mercury vehicles indicates a communication problem between the vehicle's engine control module (ECM) and the All Terrain Control Module (ATCM). Common causes include Corroded or loose wiring connections between the ECM and ATCM, Faulty communication network components (e.g., CAN bus), Malfunctioning ECM or ATCM. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
U0138 Mercury indicates Lost Communication With All Terrain Control Module.
Common causes
Common causes include Corroded or loose wiring connections between the ECM and ATCM, Faulty communication network components (e.g., CAN bus), Malfunctioning ECM or ATCM.
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
What is this?
Table of contents Created and updated by William Orellana on Sep 11, 2024
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Code U0138 Mercury Description

The U0138 diagnostic trouble code (DTC) for Mercury vehicles indicates a communication problem between the vehicle's engine control module (ECM) and the All Terrain Control Module (ATCM). The ATCM is responsible for managing the vehicle's all-wheel drive (AWD) or four-wheel drive (4WD) system, depending on the vehicle's configuration. When the ECM cannot establish communication with the ATCM, it can lead to a variety of issues affecting the vehicle's performance and safety.

OBDII Code U0138 Mercury - Lost Communication With All Terrain Control Module
U0138 Mercury Code - Lost Communication With All Terrain Control Module

Common Causes of U0138 Mercury

  1. Corroded or loose wiring connections between the ECM and ATCM
  2. Faulty communication network components (e.g., CAN bus)
  3. Malfunctioning ECM or ATCM
  4. Water intrusion or physical damage to wiring harnesses
  5. Electrical issues in the vehicle's system

Symptoms of U0138 Mercury

  1. Illumination of the check engine light on the dashboard
  2. Reduced traction control or stability in slippery road conditions
  3. Inoperative AWD or 4WD system
  4. Difficulty shifting between drive modes (e.g., from 2WD to AWD)

How to Fix U0138 Mercury

  1. Perform a comprehensive diagnostic scan to confirm the U0138 code and identify the specific communication issue.
  2. Inspect wiring harnesses, connectors, and components for any signs of damage, corrosion, or loose connections.
  3. Test the ECM and ATCM for proper functionality and communication signals.
  4. Repair or replace faulty wiring, connectors, or components as needed to restore communication between the ECM and ATCM.
  5. Clear the DTC and perform a road test to verify that the issue has been resolved and the AWD or 4WD system operates correctly.

Cost to Fix U0138 Mercury

The typical repair costs for addressing the U0138 code can vary depending on the extent of the issue, the specific components that require repair or replacement, and labor rates at auto repair shops. In general, resolving communication problems between the ECM and ATCM may range from $200 to $500, including parts and labor. However, it's advisable to consult with a qualified mechanic or dealership for a more accurate estimate based on the vehicle's make and model, as well as the local labor rates. Keep in mind that additional diagnostic time may be necessary to pinpoint the exact cause of the communication failure, potentially affecting the overall repair costs.

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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 U0138 Mercury Code

1. What are common symptoms of OBDII code U0138 "Lost Communication With All Terrain Control Module" in a Mercury?

- Common symptoms include the ABS warning light or traction control light illuminating on the dashboard, loss of traction control functionality, and potential difficulty in shifting gears.

2. What are the possible causes of U0138 code in a Mercury?

- The U0138 code can be triggered by issues such as damaged wiring or connectors, a faulty All Terrain Control Module, a software glitch, or a communication bus problem within the vehicle.

3. How can I diagnose the U0138 code in my Mercury?

- Diagnosis typically involves using an OBDII scanner to retrieve the code, inspecting the wiring and connectors related to the All Terrain Control Module, and checking for any other related fault codes.

4. Can I continue driving my Mercury with the U0138 code present?

- It is not recommended to drive your Mercury with the U0138 code active, as it can affect the vehicle's traction control system and potentially compromise safety.

5. How can I repair the U0138 code in my Mercury?

- Repairing the U0138 code may involve fixing any damaged wiring or connectors, replacing the All Terrain Control Module if necessary, and clearing the code with the OBDII scanner.

6. Is it possible to reset the U0138 code in a Mercury without fixing the underlying issue?

- While you can clear the code with an OBDII scanner, it will likely return if the root cause of the communication error with the All Terrain Control Module is not addressed.

7. Will the U0138 code cause my Mercury to fail an emissions test?

- The U0138 code itself may not directly cause your Mercury to fail an emissions test, but it indicates a problem that should be fixed to ensure the vehicle's overall performance and emissions compliance.

8. Can extreme weather conditions trigger the U0138 code in a Mercury?

- Extreme weather conditions such as excessive heat or cold can potentially affect the All Terrain Control Module and lead to a communication error triggering the U0138 code.

9. How long does it take to repair the U0138 code in a Mercury?

- The time to repair the U0138 code can vary depending on the specific cause of the issue, but it may take a few hours to a day for diagnosis, parts replacement, and clearing the code.

10. Should I attempt to fix the U0138 code in my Mercury myself, or seek professional help?

- It is recommended to seek professional help from a qualified mechanic or dealership to diagnose and repair the U0138 code, as it involves complex electrical systems that require specialized knowledge and tools.

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