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SPN 100 FMI 18

Engine Oil Pressure — Value too low (moderately severe).
The reading is below normal at a middle warning level — more serious than FMI 17, less than FMI 1.

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

What FMI 18 usually points to: A developing under-condition that often precedes a derate. More on FMI 18.

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. Low oil level
  2. Failed oil pressure sensor or wiring
  3. Worn oil pump or bearings
  4. Oil diluted with fuel or coolant
  5. Clogged pickup or filter

Checks & fixes (easiest first)

  1. Check oil level and condition (smell for fuel, look for milky coolant)
  2. Verify actual pressure with a mechanical gauge before replacing parts
  3. Inspect sensor connector and wiring
  4. Check for related oil temperature codes

FAQ

What does SPN 100 FMI 18 mean?

Engine Oil Pressure — value too low (moderately severe). The reading is below normal at a middle warning level — more serious than FMI 17, less than FMI 1.

Is SPN 100 FMI 18 serious?

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

What should I check first for SPN 100 FMI 18?

Check oil level and condition (smell for fuel, look for milky coolant); Verify actual pressure with a mechanical gauge before replacing parts; Inspect sensor connector and wiring.