U0104 Trouble Code: Meaning, Symptoms, Causes & Fixes

If you’re seeing a U0104 trouble code on your car’s dashboard, you’re likely seeking a solution to clear it.

This guide will walk you through what this code means, the symptoms it causes, and how to fix it.

In my years as a mechanic, I’ve tackled the U0104 issue numerous times—trust me, it’s fixable.

We’ll also delve into common causes that trigger this code and effective troubleshooting steps that you can perform to resolve the issue quickly and efficiently.

Time to roll up our sleeves and get to the heart of the matter.

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What Does U0104 Trouble Code Mean?

The U0104 trouble code signals a communication failure between the vehicle’s engine control module (ECM) and the cruise control module.

When this code appears, it means the ECM cannot send or receive messages from the cruise control module over the vehicle’s internal network, known as the Controller Area Network (CAN) bus.

In simpler terms, your car’s brain can’t talk to the part that controls the cruise function.

This disruption can lead to the inability to engage or operate cruise control, which might not sound critical until you’re trying to maintain a steady speed during a long drive—then it becomes a real hassle.

The communication error could be intermittent or constant. An intermittent issue might cause the cruise control to fail occasionally, then function correctly at other times.

A constant communication failure means the cruise control might not work at all until the issue is resolved.

This code is more common in vehicles with advanced electronic systems, where multiple modules communicate to control various features like speed regulation and automated safety systems.

Without proper communication between these systems, features that rely on precise control inputs, like adaptive cruise control, may become unavailable, impacting the vehicle’s functionality and your driving experience.

Addressing a U0104 code quickly is crucial not just for convenience but also to ensure your vehicle’s electronic systems function as designed.

Ignoring this problem could lead to further complications with electronic systems, especially if the root cause relates to broader issues within the CAN bus.

Remember, while cruise control might seem like a luxury, the underlying issue points to a larger problem that deserves attention.

U0104 Trouble Code Symptoms

When the U0104 trouble code appears, you might notice several disruptions. Here’s a rundown of the symptoms:

• Cruise control not working: The most direct symptom; your cruise control may fail to activate or operate correctly.
• Check engine light on: This might illuminate if the system detects a communication problem.
• Other related systems may malfunction: Systems that rely on CAN bus communication, like automatic braking or lane keep assist, might also be affected.
• Vehicle performance issues: In some cases, overall vehicle performance might degrade if the communication issue affects other critical control modules.
• Error messages on the dashboard: You may see error messages or warnings related to cruise control or other systems.

U0104 Trouble Code Causes

The U0104 trouble code can be triggered by several factors. Here are the main culprits:

• Faulty cruise control module: The module itself may be defective or failing.
• Damaged wiring or connectors: Look for issues in the wiring or connectors between the ECM and the cruise control module.
• Problems with the CAN bus network: Any disruption or fault in the CAN bus can prevent proper communication.
• Faulty ECM: A rare but possible cause is a malfunction within the engine control module itself.
• Software needing updates: Sometimes, the vehicle’s software may need an update to ensure proper communication between modules.

How To Fix A U0104 Trouble Code

Fixing a U0104 trouble code involves a systematic approach to diagnosing and addressing communication issues within your vehicle’s network. Here’s how to tackle it:

1. Diagnostic Scan

Start with a full diagnostic scan using an OBD-II scanner. This will confirm the U0104 code and might reveal additional codes that can help pinpoint the problem.

2. Visual Inspection

Inspect all related wiring and connectors. Look for any signs of damage like fraying, corrosion, or loose connections that could disrupt communication between the ECM and the cruise control module.

3. Check the Cruise Control Module

Test the cruise control module if possible. In some cases, replacing a faulty cruise control module is necessary if it fails testing.

4. Examine the CAN Bus

Since the CAN bus is the communication highway for your vehicle’s electronic systems, ensure it’s functioning correctly. This may require specialized equipment to test the network’s integrity.

5. Repair or Replace Components

Based on your findings from the diagnostic and visual checks, repair or replace damaged wiring, connectors, or components.

6. Software Update

Check if there is a software update available for your vehicle’s ECM or cruise control system. Updating the software can sometimes resolve communication issues.

7. Clear the Code and Test Drive

After repairs, clear the trouble code from the system using an OBD-II scanner, then take the vehicle for a test drive to ensure the cruise control functions properly and the code does not reappear.

8. Professional Help

If the problem persists, it may be best to consult a professional mechanic who can perform more advanced diagnostics and repairs.

By following these steps, you can address the U0104 trouble code effectively and restore full functionality to your vehicle’s cruise control and related systems.

Conclusion

Now that you’re equipped with the knowledge of what U0104 means and how to tackle it, you’re set to handle it yourself.

Have you encountered this issue before in your vehicle?

Feel free to share your experiences or tips in the comments below. Let’s help each other out!