Detailed guide for SPN 100 FMI 4
Back to top ↑What SPN 100 FMI 4 means
SPN 100 identifies engine oil pressure. FMI 4 indicates voltage below normal or a signal shorted toward a low source.
This is primarily an electrical diagnostic condition. A very low electronic reading does not by itself prove that the engine has mechanically lost oil pressure.
What to check first
Inspect the oil-pressure sensor connector and harness for damaged insulation, corrosion, terminal problems or a short to ground.
Check sensor supply, ground and signal voltage using the OEM wiring diagram.
If necessary, independently verify actual engine oil pressure before making mechanical repairs.
Diagnose electrical SPN 100 faults before assuming the oil pump or internal engine components have failed.
Mechanic community notes for SPN 100 FMI 4
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