Fault-Code Library · Vehicle network
U0100: Lost communication with engine control module
One or more modules stopped receiving expected messages from the engine controller.
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.
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