U0073: Control Module Communication Bus "A" Off
U0073 means Control Module Communication Bus "A" Off. A module has stopped communicating on bus "A" because it detected too many errors (bus-off).
CodeU0073
SystemNetwork communication
SeverityHigh
TypeGeneric network communication
Can I keep driving? Limit driving and diagnose promptly. Continued driving can cause damage, stalling or limp mode.
Common symptoms
- Several warning lights at once
- Modules or features not working
- Possible no-start or limp mode, depending on the module
Possible causes
- Low battery voltage or poor ground
- Blown fuse or lost power to the module
- Damaged CAN bus wiring or connector
- Failed module
- Aftermarket accessories tapped into the network
How to diagnose U0073
- Check battery voltage and grounds first.
- Scan all modules to see which ones do not respond.
- Check power and ground to the non-responding module.
- Measure resistance between CAN-H and CAN-L at the diagnostic connector with the battery disconnected; many high-speed CAN networks read about 60 Ω.
- Inspect wiring and connectors along the bus.
What the code means, digit by digit
UNetwork communication0Generic (SAE) code0Sub-system73Specific fault
Generic codes have the same definition on every OBD-II vehicle (petrol cars from model year 1996 in the US, 2001 in the EU; diesels later). Manufacturers can add their own enhanced codes; those are not listed here.
Related codes
- U0001 High Speed CAN Communication Bus
- U0100 Lost Communication With ECM/PCM "A"
- U0101 Lost Communication With TCM
- U0121 Lost Communication With Anti-Lock Brake System (ABS) Control Module
- U0140 Lost Communication With Body Control Module
- U0155 Lost Communication With Instrument Panel Cluster (IPC) Control Module
General guidance only. Fault codes describe what the engine computer saw, not which part failed: confirm with testing before replacing parts, and follow the vehicle's service information.