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SPN 788 FMI 7 — Clutch actuator not responding mechanically

What it means: Clutch actuator not responding mechanically.

How serious / can you keep driving: Serious. Power derate likely — plan to stop soon.

Check first: Inspect clutch wear

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SeriousDrivetrain & TransmissionPower derate likely — plan to stop soon

Applies to: Eaton · Volvo · UltraShift PLUS common

What SPN 788 FMI 7 means

Clutch actuator not responding mechanically.

How serious is it?

Serious. Power derate likely — plan to stop soon.

Most likely causes

  1. Failed clutch actuator
  2. Clutch worn out
  3. Mechanical bind
  4. Clutch actuator
  5. Clutch worn
  6. Linkage

First moves (roadside)

  1. Inspect clutch wear
  2. Check actuator
  3. Inspect clutch
  4. Actuator test

Common misdiagnoses

  • Replacing actuator when clutch is worn

FAQ

What does SPN 788 FMI 7 mean?

Clutch actuator not responding mechanically.

How serious is SPN 788 FMI 7?

Serious — Power derate likely — plan to stop soon.

What's the most likely cause of SPN 788 FMI 7?

The most common cause is: Failed clutch actuator. Other possibilities include Clutch worn out; Mechanical bind; Clutch actuator; Clutch worn; Linkage.

Can I keep driving with SPN 788 FMI 7?

Power derate likely — plan to stop soon. When in doubt, get a qualified mobile diesel tech on the truck before continuing.

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Related codes

Codes that commonly appear alongside SPN 788 FMI 7, or share the same subsystem.

Same symptom: Won't shift

Other codes that show up as a truck that won't take a gear or drops out of one.

All Drivetrain & Transmission codes

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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.