OBD Code U0104: Lost Communication With Cruise Control Module

Quick Answer

What Does U0104 Mean?

The diagnostic trouble code U0104 indicates that your vehicle’s main control module (usually the engine control module or body control module) has lost communication with the cruise control module. This is a network communication fault code that falls under the “U” category, which covers vehicle network faults.

Modern vehicles use a CAN (Controller Area Network) bus system to allow different modules to communicate with each other. When the cruise control module stops responding to communication attempts, the vehicle’s diagnostic system detects this loss of signal and sets the U0104 code. This code is distinct from performance codes because it’s about the inability to communicate, not necessarily a functional failure of the cruise control system itself.

Common Symptoms

• Cruise control button becomes unresponsive or non-functional
• Check Engine Light (CEL) illuminates on the dashboard
• Cruise control feature is disabled or unavailable
• Vehicle may go into a reduced power or limp mode (in some cases)
• No error messages displayed when attempting to use cruise control
• Other vehicle systems may be affected if the CAN bus is compromised
• Possible intermittent issues that come and go

Possible Causes

1. Faulty Cruise Control Module – The most common cause. The module may have internal failures, corrosion, or component degradation that prevents it from communicating on the CAN bus.
2. Damaged CAN Bus Wiring – Broken, corroded, or pinched wires in the CAN bus network can interrupt communication between modules.
3. Loose or Corroded Connectors – Poor connections at the cruise control module, body control module, or CAN bus connectors can cause intermittent or complete communication loss.
4. Battery or Charging System Issues – Low voltage or unstable power supply can prevent the cruise control module from operating properly.
5. Engine Control Module (ECM) Failure – If the main ECM is faulty, it may not properly communicate with other modules on the network.
6. Body Control Module (BCM) Malfunction – The BCM acts as a gateway for many vehicle systems and may have communication issues.
7. Software/Firmware Issues – Outdated or corrupted module software can cause communication problems.
8. Multiplex Wiring Harness Damage – Damage to the main CAN bus wiring harness from accidents, rodents, or wear.
9. Blown Fuses or Relays – A blown fuse or relay related to the cruise control circuit can prevent module operation.

Diagnostic Steps

Step 1: Scan the Vehicle

Connect a diagnostic scanner to the OBD-II port and retrieve all stored and pending codes. Note any additional codes that may help identify the root cause. U0104 often appears alongside other network communication codes.

Step 2: Perform a Visual Inspection

Inspect the cruise control module (typically located under the steering column or in the dashboard) for signs of damage, corrosion, or loose connectors. Check the CAN bus wiring harness for visible damage, cuts, or pinching. Look for water damage or corrosion on connectors.

Step 3: Check Battery Voltage

Measure the battery voltage with a multimeter. It should read between 12.6V and 14.4V. Low voltage can cause communication issues. If the voltage is low, test the alternator and battery health.

Step 4: Inspect Connectors and Wiring

Disconnect and reconnect the cruise control module connector several times to ensure good contact. Clean any corrosion with electrical contact cleaner. Check for bent pins or damaged connectors. Inspect the CAN bus wiring (typically two twisted wires labeled CAN High and CAN Low) for damage.

Step 5: Test CAN Bus Communication

Using a diagnostic scanner, test the CAN bus voltage and signal integrity. The CAN bus should show proper voltage levels and signal patterns. If communication is absent, the issue is likely in the wiring or a major module failure.

Step 6: Check Fuses and Relays

Locate the fuse and relay for the cruise control system (consult your vehicle’s service manual for locations). Test or replace any blown fuses. Swap relays with known-good units to rule out relay failure.

Step 7: Module Replacement or Repair

If all wiring and connections test good, the cruise control module itself is likely faulty and requires replacement. In some cases, the ECM or BCM may need reprogramming or replacement.

Step 8: Clear the Code and Test

After repairs, clear the diagnostic code using your scanner and test the cruise control function. Drive the vehicle to ensure the code does not return.

Repair Cost Estimates

• Fuse or Relay Replacement: $20 – $100 (parts and labor)
• Wiring Repair or Connector Cleaning: $50 – $300 (depending on severity and location)
• Cruise Control Module Replacement: $300 – $800 (parts and labor, varies by vehicle make/model)
• Engine Control Module (ECM) Replacement: $500 – $1,500+ (includes programming)
• Body Control Module (BCM) Replacement: $400 – $1,200+ (includes programming)
• Full CAN Bus Wiring Harness Replacement: $600 – $1,500+ (labor-intensive)
• Diagnostic Service: $100 – $200 (to identify the exact cause)

Note: Costs vary significantly based on vehicle make, model, year, and whether the repair is performed at a dealership or independent shop.

Can I Still Drive?

Safety Assessment: Generally Safe to Drive

In most cases, U0104 is not a critical safety issue and you can continue driving your vehicle. The loss of cruise control communication does not affect your ability to accelerate, brake, or steer manually. However, there are some important considerations:

• Cruise Control Unavailable: You will not be able to use the cruise control feature until the issue is resolved.
• Potential Secondary Issues: Depending on your vehicle’s architecture, a CAN bus communication problem could potentially affect other systems. Monitor your dashboard for additional warning lights.
• Limp Mode Risk: Some vehicles may enter reduced power mode if multiple modules lose communication. If this occurs, have the vehicle serviced immediately.
• Intermittent Issues: If the problem is intermittent, it may worsen over time. Address it sooner rather than later to prevent complete system failure.

It is recommended to have the vehicle diagnosed and repaired within a reasonable timeframe to restore full functionality and prevent potential cascade failures of other vehicle systems.

Frequently Asked Questions