Detailed guide for SPN 101 FMI 3
Back to top ↑What SPN 101 FMI 3 means
SPN 101 identifies crankcase pressure. FMI 3 indicates that the crankcase pressure sensor circuit voltage is above the calibrated threshold.
Detroit describes SPN 101 FMI 3 as a crankcase pressure sensor circuit failed-high condition.
What to check first
Inspect the sensor and harness connectors for corrosion, damaged terminals or wiring damage.
Check the crankcase pressure sensor circuit for a short to power or an open ground.
If other FMI 3 sensor circuit faults are active at the same time, diagnose shared electrical circuits before replacing individual sensors.
Diagnostic note
On the documented Detroit application, this electrical fault illuminates the check-engine lamp but does not itself command an engine reaction.
Do not assume that high sensor voltage means actual crankcase pressure is mechanically high. Confirm the electrical circuit first.
Mechanic community notes for SPN 101 FMI 3
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