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SPN 749 FMI 7 — Gear selection failure
SeriousTransmissionPower derate likely — plan to stop soon
Applies to: Eaton · Volvo
Gear selection failure.
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
- Shift actuator
- Air supply low (AMT)
- Synchronizer issue
- Low air pressure
- Synchronizer
First moves (roadside)
- Check air pressure
- Actuator operation
FAQ
What does SPN 749 FMI 7 mean?
Gear selection failure.
How serious is SPN 749 FMI 7?
Serious — Power derate likely — plan to stop soon.
What's the most likely cause of SPN 749 FMI 7?
The most common cause is: Shift actuator. Other possibilities include Air supply low (AMT); Synchronizer issue; Low air pressure; Synchronizer.
Can I keep driving with SPN 749 FMI 7?
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.