OBD-II code · Network
U0028 Vehicle Communication Bus A
Generic fault on vehicle communication bus A. The controller flags an unspecified electrical or protocol fault on this bus segment that does not match the more specific U0xxx subcodes.
Is it safe to drive with U0028?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelyIntermittent CAN wiring fault
- PossibleMarginal node corrupting traffic
- Less likelyGateway module routing CAN messages incorrectly
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1–5 h
- Emissions test
- Usually unaffected
- Parts involved
- Can Bus Wiring, Control Module
Related codes
- U0029Vehicle Communication Bus B
- U0037Vehicle Communication Bus B
- U0046Vehicle Communication Bus C
- U0055Vehicle Communication Bus D
- U0064Vehicle Communication Bus E
- U0089Vehicle Communication Bus G
- U009BVehicle Communication Bus I
- U009DVehicle Communication Bus J
- U0025Low Speed CAN Communication Bus (-) Open
- U0026Low Speed CAN Communication Bus (-) Low
- U0027Low Speed CAN Communication Bus (-) High
- U0030Powertrain Sensor Data Bus
- U0031Vehicle Communication Bus C (+) Open
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.