U0073: Control Module Communication Bus Off

What Does U0073 Mean?

Code U0073 indicates that a control module has detected that the communication bus has gone offline. This means the CAN bus has experienced enough errors that the module has entered a bus-off state, effectively disconnecting from all other modules. This is a protective mechanism but results in loss of module communication.

Common Causes

• CAN bus wiring short to power or ground
• Failed control module flooding the bus with errors
• Water intrusion into a wiring connector
• CAN bus backbone wire damage from collision or corrosion
• Missing CAN bus termination resistor

Symptoms

• Multiple warning lights on dashboard
• Loss of multiple vehicle systems
• Instrument cluster may go dark or show errors
• Vehicle may enter limp mode
• No communication with some modules during scan

Diagnostic Steps

1. 1Attempt to communicate with all modules and note which are offline
2. 2Check CAN bus termination resistance (should be about 60 ohms total)
3. 3Inspect CAN bus wiring at all accessible connectors and splices
4. 4Systematically unplug modules to isolate the one causing bus errors
5. 5Check for water intrusion at known problem areas
6. 6Use an oscilloscope to analyze CAN bus signals for error frames

Estimated Repair Cost

Frequently Asked Questions