Network, generic

U0001 High Speed CAN Communication Bus

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Bus pair chafed, pinched or crushed in the harness
Corroded, loose or bent pins at a module or splice connector
One module or its transceiver disturbing the whole bus
History entry after a voltage dip or tester connected with ignition on

Symptoms

  • 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

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–1,500
Time1–8 h

Typical range across vehicles; the real cost depends on what the testing finds.

What to check first

  1. Check battery voltage
  2. Measure CAN resistance
  3. Disconnect modules one at a time to find the culprit

Parts involved

can bus wiringcan terminating resistorcontrol module

Related codes

U0002U0003U0009U0010U0073

References: saabwisonline.com, gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov.