OBD-II code · Network
U0009 High Speed CAN Communication Bus (-) Shorted to Bus (+)
CAN-High and CAN-Low are shorted together. The differential signal collapses to zero and the bus controller can no longer separate dominant from recessive bits, so all communication stops.
Is it safe to drive with U0009?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyCAN-H and CAN-L shorted together
- PossiblePinched harness behind a module
- Less likelyGateway module routing CAN messages incorrectly
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
- Can High Wire, Can Low Wire, Module Connector
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.