Lost Communication With ECM/PCM
What it means
A module has lost CAN-bus communication with the engine control module.
Symptoms
Multiple warning lights, no-start, drivability problems.
Common causes
CAN wiring fault, connector corrosion, failing module, or power/ground issue.
Recommended action
Inspect CAN wiring, connectors, and module power/grounds — diagnosis usually needs a scan tool.
Related codes
FAQ — U0100
What does code U0100 mean?
Lost Communication With ECM/PCM. A module has lost CAN-bus communication with the engine control module.
What are the symptoms of U0100?
Multiple warning lights, no-start, drivability problems.
What causes U0100?
CAN wiring fault, connector corrosion, failing module, or power/ground issue.
What should I do about U0100?
Inspect CAN wiring, connectors, and module power/grounds — diagnosis usually needs a scan tool.
General reference based on the SAE J2012 standard. Exact causes for your vehicle may differ — when in doubt, consult a workshop.
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