U0003High Speed CAN Communication Bus (+) Open
- Generic OBD-II code · Network
- Can trigger limp mode
- How the car detects it
- U0003 reports a break in the (+) wire of the high-speed CAN, which GM and FCA also call CAN-High. At rest this line idles near 2.5 V and is lifted about one volt for each dominant bit. Once it is cut, modules on the far side of the break lose the differential pair and drop out, while nodes on the intact section may keep talking. Standard high-speed transceivers cannot report a wire interruption on their own, as NXP points out, so whether a module stores U0003 depends on its own monitoring. Harley-Davidson lists U0003 together with U0001 as history codes in the ABS unit of 2017 Touring models when the TechLink interface was plugged in with the ignition already on; there no repair is due. Genuine breaks come from chafing, pushed-back terminals or corrosion.
- What you may notice
- Modules beyond the break no longer reachable
- Several warnings and fallback modes at once
- Fault appears or disappears when the harness is moved
- Likely causes
- LikelyCAN-High conductor broken at a flex point or after a repair
- PossibleCAN-High terminal pushed back or corroded in a connector
- RareDiagnostic interface connected with ignition on (history code only)
- Repair
- Hard · Usually a job for a workshop.Typical cost: €80 – €800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.