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SPN 111 FMI 18

Coolant Level — 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: Coolant level in the expansion tank or radiator, from a level probe or switch. More on SPN 111.

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

Severity

HIGH — limit use, diagnose now

Low coolant can lead to overheating and head damage. Top off and find the leak before working hard.

Likely causes

  1. Coolant leak (hoses, radiator, water pump, EGR cooler)
  2. Coolant level sensor dirty or failed
  3. Wiring fault

Checks & fixes (easiest first)

  1. Check actual level when cold
  2. Look for external leaks and white exhaust smoke
  3. Clean or test the level probe
  4. Pressure-test the cooling system

FAQ

What does SPN 111 FMI 18 mean?

Coolant Level — 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 111 FMI 18 serious?

Low coolant can lead to overheating and head damage. Top off and find the leak before working hard.

What should I check first for SPN 111 FMI 18?

Check actual level when cold; Look for external leaks and white exhaust smoke; Clean or test the level probe.