OBD codes / U0100
U0100
SeriousLost Communication With ECM/PCM A
Address promptly — can worsen or affect drivability.
Likely causes
- wiring/connector fault
- module failure
- power/ground issue
Common fixes
- inspect CAN wiring
- check module power/grounds
Seeing U0100 on your car? Get a diagnosis specific to your exact year, make and model.
Diagnose U0100 for my vehicleGeneric OBD-II reference. Manufacturer-specific behavior varies — confirm with a scan tool and, for safety-related codes, a professional inspection.