OBD-II code · Network
U0018 Medium Speed CAN Communication Bus (+) Low
CAN-High on the medium-speed bus is shorted to ground. The differential pair cannot work, all body and comfort nodes drop offline at the same time.
Is it safe to drive with U0018?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelyCAN-High 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
- 0.8–4 h
- Emissions test
- Usually unaffected
- Parts involved
- Can High Wire
Related codes
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.