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SPN 788 FMI 5 — Clutch actuator open circuit
SeriousTransmissionPower derate likely — plan to stop soon
Applies to: Eaton · Volvo · Self-adjusting clutch
Clutch actuator open circuit.
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
- Open motor
- Wiring
- Connector
- Open motor/coil
First moves (roadside)
- Resistance check motor
- Check drive wires
- Resistance check
FAQ
What does SPN 788 FMI 5 mean?
Clutch actuator open circuit.
How serious is SPN 788 FMI 5?
Serious — Power derate likely — plan to stop soon.
What's the most likely cause of SPN 788 FMI 5?
The most common cause is: Open motor. Other possibilities include Wiring; Connector; Open motor/coil.
Can I keep driving with SPN 788 FMI 5?
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.