OBD-II code · Network
U0003 High Speed CAN Communication Bus (+) Open
The CAN-High line of the high-speed bus is open. Without the differential pair, the controller cannot decode any traffic and reports loss of all participating modules at once. Often follows a wiring repair, accident damage, or a corroded connector pin.
Is it safe to drive with U0003?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyCAN-High wire broken or pin pushed back
- PossibleCorroded module connector
- PossibleHarness damage after repair or accident
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, Module Connector, Can Transceiver
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.