FMI 18 — Data valid but below normal operating range — moderately severe level
Real reading, clearly low. The stage before a derate or shutdown.
Common causes
- Leak, restriction on the supply side or worn pump
- Regulator stuck open
- Sensor drift
What to test, in order
- Confirm with a mechanical gauge
- Pressure- or leak-test the supply circuit
- Test the pump and regulator output
- Escalate immediately if the value keeps falling
Codes we document with FMI 18
SPN 100 FMI 18Oil pressure below critical · InternationalSPN 157 FMI 18Injector rail pressure below spec · VolvoSPN 157 FMI 18Injector metering rail 1 pressure below normal - moderately severe · CATSPN 157 FMI 18Injector metering rail 1 pressure below normal - moderately severe · DetroitSPN 157 FMI 18Injector metering rail 1 pressure below normal - moderately severe · InternationalSPN 157 FMI 18Injector metering rail 1 pressure below normal - moderately severe · PACCARSPN 157 FMI 18Injector metering rail 1 pressure below normal - moderately severe · MERCEDESSPN 157 FMI 18Injector metering rail 1 pressure below normal - moderately severe · MackSPN 157 FMI 18Injector metering rail 1 pressure below normal - moderately severe · CumminsSPN 1692 FMI 18Turbocharger underboost · PACCARSPN 3050 FMI 18SCR catalyst conversion efficiency below normal · CATSPN 3050 FMI 18SCR catalyst conversion efficiency below normal · DetroitSPN 3050 FMI 18SCR catalyst conversion efficiency below normal · InternationalSPN 3050 FMI 18SCR catalyst conversion efficiency below normal · PACCARSPN 3050 FMI 18SCR catalyst conversion efficiency below normal · MERCEDESSPN 3050 FMI 18SCR catalyst conversion efficiency below normal · VolvoSPN 3050 FMI 18SCR catalyst conversion efficiency below normal · MackSPN 3050 FMI 18SCR catalyst conversion efficiency below normal · CumminsSPN 4364 FMI 18SCR conversion efficiency low · Mack
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