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SPN 100 FMI 4

Engine Oil Pressure — Voltage below normal or shorted low.
The sensor circuit voltage is lower than it should ever be, usually near zero.

What the SPN covers: Engine oil pressure measured in the main oil gallery. More on SPN 100.

What FMI 4 usually points to: Signal wire shorted to ground, a lost 5 V reference, or an open signal wire on a pulled-down circuit. More on FMI 4.

Severity

STOP — shut down if the condition is real

If oil pressure is truly low, shut the engine down. Running with low oil pressure can wreck bearings in minutes.

Likely causes

1. Wiring or connector fault in this circuit (most common for electrical FMIs)
2. Low oil level
3. Failed oil pressure sensor or wiring
4. Worn oil pump or bearings
5. Oil diluted with fuel or coolant
6. Clogged pickup or filter

Checks & fixes (easiest first)

1. Inspect the connector and harness for this circuit: corrosion, water, chafing, backed-out pins
2. Check the reference voltage, ground and signal at the component per OEM pin-out
3. Check oil level and condition (smell for fuel, look for milky coolant)
4. Verify actual pressure with a mechanical gauge before replacing parts
5. Inspect sensor connector and wiring
6. Check for related oil temperature codes

FAQ