U0100 — Lost Communication with ECM/PCM
Seen on: All trucks
Lost Communication with ECM/PCM. Common causes: CAN bus failure, ECM power loss, wiring issue.
Your code rides along, so nearby mechanics see the fault before they quote you.
How serious is it?
Critical. Stop as soon as it's safe.
Most likely causes
- CAN bus failure
- ECM power loss
- wiring issue
- Ground fault
- blown fuse
- corroded connector J1939
FAQ
Lost Communication with ECM/PCM. Common causes: CAN bus failure, ECM power loss, wiring issue.
Critical — Stop as soon as it's safe.
The most common cause is: CAN bus failure. Other possibilities include ECM power loss; wiring issue; Ground fault; blown fuse; corroded connector J1939.
Stop as soon as it's safe. When in doubt, get a qualified mobile diesel tech on the truck before continuing.
Find a mechanic or related guides
General diagnostic guidance for diesel engines (Cummins, Detroit, PACCAR, Volvo, Mack and more). Not a substitute for a scan-tool diagnosis on your specific truck.