Uxxxx · Network
U0073
Control Module Communication Bus "A" Off
CriticalNetwork ECU
What it means
The high-speed CAN bus has gone silent or is showing electrical fault. All modules on that bus segment are affected.
Common causes
Listed in rough order of frequency. Verify with vehicle-specific service info before parts replacement.
- 01CAN-H or CAN-L wire shorted to ground or to each other
- 02Failed CAN termination resistor
- 03Module on the bus pulling the entire bus down (intermittent — disconnect modules one at a time)
- 04Damaged connector at a gateway module
Affected systems
ECUs and subsystems that report or are affected by this code.
CAN gatewayEvery module on the affected bus
Get vehicle-specific diagnosis for U0073
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Ask the forums about U0073Critical-severity code
This code typically prevents the vehicle from starting, running normally, or operating safely. Diagnose carefully before clearing — clearing without fixing the root cause often masks deeper problems.