OBD-II code · Network
U0049 Vehicle Communication Bus C (+) Low
Bus C high-side line voltage below expected range. 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 U0049?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyWire 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
- 1–6 h
- Emissions test
- Usually unaffected
- Parts involved
- Bus C Wiring
Related codes
- U0058Vehicle Communication Bus D (+) Low
- U0067Vehicle Communication Bus E (+) Low
- U0079Vehicle Communication Bus B (+) Low
- U008CVehicle Communication Bus G (+) Low
- U0095Vehicle Communication Bus H (+) Low
- U0046Vehicle Communication Bus C
- U0047Vehicle Communication Bus C Performance
- U0048Vehicle Communication Bus C (+) Open
- U0050Vehicle Communication Bus E (+) Open
- U0051Vehicle Communication Bus C (-) Open
- U0052Vehicle Communication Bus C (-) Low
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.