U0001High Speed CAN Communication Bus
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- U0001 is the umbrella code for trouble on the high-speed CAN, the fast two-wire network joining engine, transmission, brake and steering modules. GM/Saab logs it once a module's transmit error counter climbs past 255: that module disconnects itself, stops sending and works with substitute values. Older GM calibration tables treat it as a bus-off, Type B after 5 s (2006 V8 ECM), and a 2006 five-speed TCM flags it after 64 bus-off events with the MIL on at once. FCA names U0001 CAN C Bus (Ram 1500 steering gear harness, Jeep Compass wiring crushed by a console bolt); Volvo and Mack trucks store it together with U0010 in the aftertreatment module, with MIL and possible derate. Usually several modules report it at once; individual wire faults have their own codes U0003 to U0009.
- What you may notice
- Several warning lamps and messages at the same time
- Scan tool reaches some modules only or none at all
- Shifting, steering assist or brake functions in fallback mode
- Many lost-communication codes stored alongside
- Likely causes
- LikelyBus pair chafed, pinched or crushed in the harness
- LikelyCorroded, loose or bent pins at a module or splice connector
- PossibleOne module or its transceiver disturbing the whole bus
- RareHistory entry after a voltage dip or tester connected with ignition on
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €80 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.