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SPN 625 FMI 9 — J1939 proprietary datalink lost
SeriousEnginePower derate likely — plan to stop soon
Applies to: Navistar · Paccar · Volvo
J1939 proprietary datalink lost.
Don't risk it — get a diesel tech on the truck.
Your SPN/FMI rides along, so nearby mechanics see the fault before they quote you.
How serious is it?
Serious. Power derate likely — plan to stop soon.
Most likely causes
- Bus issue
- ECU offline
- CAN bus issue
- Another ECU offline
- Datalink issue
First moves (roadside)
- Check terminations
- Ping ECUs
- Ping all ECUs
- Scan all ECUs for presence
FAQ
What does SPN 625 FMI 9 mean?
J1939 proprietary datalink lost.
How serious is SPN 625 FMI 9?
Serious — Power derate likely — plan to stop soon.
What's the most likely cause of SPN 625 FMI 9?
The most common cause is: Bus issue. Other possibilities include ECU offline; CAN bus issue; Another ECU offline; Datalink issue.
Can I keep driving with SPN 625 FMI 9?
Power derate likely — plan to stop soon. When in doubt, get a qualified mobile diesel tech on the truck before continuing.
Throwing this code right now?
Find a mechanic or related guides
General diagnostic guidance for heavy-duty diesel engines (Cummins, Detroit, PACCAR, Volvo, Mack). Not a substitute for a scan-tool diagnosis on your specific truck.