OBD-II code · Network
U0029 Vehicle Communication Bus B
Generic fault on vehicle communication bus B. Used as a catch-all for unspecified problems on a secondary CAN/comfort segment.
Is it safe to drive with U0029?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelyIntermittent 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
- 1–5 h
- Emissions test
- Usually unaffected
- Parts involved
- Can Bus Wiring, Control Module
Related codes
- U0028Vehicle Communication Bus A
- 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
- U0026Low Speed CAN Communication Bus (-) Low
- U0027Low Speed CAN Communication Bus (-) High
- U0030Powertrain Sensor Data Bus
- U0031Vehicle Communication Bus C (+) Open
- U0032Vehicle Communication Bus A (+) High
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.