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SPN 797 FMI 5 — Modulator valve — left front — open

What it means: Modulator valve — left front — open.

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

Check first: Ohm modulator valve

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SeriousBrakes, ABS & StabilityPower derate likely — plan to stop soon

Applies to: Bendix · Wabco

What SPN 797 FMI 5 means

Modulator valve — left front — open.

How serious is it?

Serious. Power derate likely — plan to stop soon.

Most likely causes

  1. Open solenoid
  2. Wire open
  3. Connector
  4. Wire

First moves (roadside)

  1. Ohm modulator valve
  2. Check drive wires
  3. Ohm and check

FAQ

What does SPN 797 FMI 5 mean?

Modulator valve — left front — open.

How serious is SPN 797 FMI 5?

Serious — Power derate likely — plan to stop soon.

What's the most likely cause of SPN 797 FMI 5?

The most common cause is: Open solenoid. Other possibilities include Wire open; Connector; Wire.

Can I keep driving with SPN 797 FMI 5?

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

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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.