Fault-Code Library · Vehicle network

U0100: Lost communication with engine control module

One or more modules stopped receiving expected messages from the engine controller.

Fault-Code Library

Common symptoms

  • •No start
  • •Multiple warning lights
  • •Intermittent shutdown
  • •Many network codes

Likely causes

  • •Low system voltage
  • •Power or ground loss at the ECU
  • •CAN wiring fault
  • •Module or gateway issue

First checks

  • •Test battery voltage and charging health
  • •Check ECU powers and grounds
  • •Map which modules can and cannot communicate

Important

A network code does not by itself prove that the engine ECU has failed.

A fault code identifies a detected condition, not a failed part. Confirm manufacturer-specific subcodes and live data.

Inspect first