OBD-II code · Network
U0031 Vehicle Communication Bus C (+) Open
The plus line of vehicle bus C is open. Modules sharing this segment drop offline. A communication loss with this module breaks any function relying on its data — diagnostic tools may show 'no response' and dependent modules can fall into limp mode.
Is it safe to drive with U0031?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelyBus-C high wire broken
- 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 High Wire
Related codes
- U0039Vehicle Communication Bus B (+) Open
- U0042Vehicle Communication Bus D (+) Open
- U0048Vehicle Communication Bus C (+) Open
- U0050Vehicle Communication Bus E (+) Open
- U0057Vehicle Communication Bus D (+) Open
- U0060Vehicle Communication Bus F (+) Open
- U0066Vehicle Communication Bus E (+) Open
- U0078Vehicle Communication Bus B (+) Open
- U008BVehicle Communication Bus G (+) Open
- U0094Vehicle Communication Bus H (+) Open
- U0028Vehicle Communication Bus A
- U0029Vehicle Communication Bus B
- U0030Powertrain Sensor Data Bus
- U0032Vehicle Communication Bus A (+) High
- U0033Vehicle Communication Bus A (-) Open
- U0034Vehicle Communication Bus A (-) Low
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.