U0104 Lost Communication with Cruise Control Module
Diagnostic trouble code U0104 indicates a loss of communication between the powertrain control module (PCM/ECM) and the cruise control module over the CAN bus. This code is set when the master module fails to receive valid messages from the cruise control module for a specified period, typically due to wiring issues, module faults, or power supply problems.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Faulty cruise control module (internal damage or software failure)
- Open or short circuit in CAN bus wiring (CAN-H or CAN-L lines)
- CAN bus terminating resistor out of specification (should be 120 ohms per terminator)
- Power supply issues to the cruise control module (blown fuse, poor ground connection)
- Corrosion in connectors or pins of the wiring harness
- Faulty PCM/ECM preventing communication
- Aftermarket electrical modifications interfering with the CAN bus
3. Symptoms You Will Notice
- Cruise control inoperative
- Check Engine Light or cruise control indicator light on
- Possible other communication-related codes
4. Step-by-Step Diagnosis
Scan for all stored codes and freeze frame data
Inspect cruise control module fuse and relay, check for power and ground at the module connector
Visually inspect CAN bus wiring for damage, corrosion, or loose connections
Measure CAN bus resistance at the module connector (should be 60 ohms with both terminators)
Check for communication by monitoring CAN bus signals with a scope or scan tool
If wiring and power are OK, suspect a faulty cruise control module or PCM
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, the vehicle is generally safe to drive, but cruise control will not work. Other systems may be affected if the communication issue is widespread.
How much does it cost to fix?▼
Diagnosis typically costs $100-$150. Repair costs vary: a blown fuse is cheap, but replacing a cruise control module can range from $200 to $600, including labor.