U0073 U0xxx · Network (U) High severity
Control Module Communication Bus Off
A module has shut down its CAN transmitter, often as self-protection after persistent errors. It may be a symptom rather than the root cause.
Severity guidance: High — stop driving and diagnose now; risk of further damage
Symptoms you will notice
- Module unreachable
- Multiple warning lamps
- Functions unavailable
Common causes
Ordered from most to least likely — start at the top.
- 1 Bus errors forcing the module off-line
- 2 Module supply voltage out of range
- 3 Internal fault
- 4 Software issue
How to diagnose it
Cheapest and least invasive first — most of these codes are not a parts problem.
- ✓ Check whether other modules are also off — if so, treat as a bus fault first.
- ✓ Verify power and earth at the silent module.
- ✓ Power-cycle the vehicle completely and rescan.
- ✓ Read any stored fault history that survives the shutdown.
Repair options
- Repair the underlying bus fault
- Restore the module supply
- Replace the module if it never recovers
U0073 — frequently asked questions
Is the module dead? +
Not necessarily. Bus-off is a protective state. After fixing the bus, most modules come back on a power cycle.
Can I force it back? +
Some tools can issue a bus-off recovery command, but if the bus is still faulty it will drop out again.
Confirm the diagnosis before you buy parts
Send us the code, freeze-frame data and the vehicle — our engineers will tell you what to test first.