OBD-II code · Network
U0077 Vehicle Communication Bus B Off
A controller on bus B has reached its transmit error limit and shut its transceiver off. All traffic on this segment stops until the cause is removed.
Is it safe to drive with U0077?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelyPersistent wiring fault on bus B
- Less likelyGateway module routing CAN messages incorrectly
- Less likelyCAN terminating resistor (120 Ω) drifted out of spec
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
- 1–6 h
- Emissions test
- Usually unaffected
- Parts involved
- Can Transceiver, Can Bus Wiring
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.