OBD-II code · Network
U0079 Vehicle Communication Bus B (+) Low
The plus line of bus B is shorted to ground. The differential signal collapses and bus traffic stops.
Is it safe to drive with U0079?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelyBus-B plus shorted to ground
- 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
- 0.8–5 h
- Emissions test
- Usually unaffected
- Parts involved
- Can High Wire
Related codes
- U0049Vehicle Communication Bus C (+) Low
- U0058Vehicle Communication Bus D (+) Low
- U0067Vehicle Communication Bus E (+) Low
- U008CVehicle Communication Bus G (+) Low
- U0095Vehicle Communication Bus H (+) Low
- U0076Control Module Communication Bus "C" Off
- U0077Vehicle Communication Bus B Off
- U0078Vehicle Communication Bus B (+) Open
- U007AControl Module Communication Bus H Off
- U007BControl Module Communication Bus I Off
- U007CControl Module Communication Bus J Off
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.