Caterpillar Fault Code
Free · no signupSPN 111 FMI 1
Warning light/Buzzer; Engine shutdown protection active; Potential coolant spray.
System
Not specified
Symptom
Warning light/Buzzer; Engine shutdown protection active; Potential coolant spray.
Diagnosis & fix steps
Engine Coolant Level - Low (Most Severe).
LOGIC: The level sensor (usually ultrasonic or conductivity) is not submerged.
ACTION: 1. Check expansion tank level visually.
2. If tank is full, unplug sensor; check for debris/film on the sensor probe.
3. Check for air pockets in the cooling system (air lock).
FIX: Top up coolant; replace Coolant Level Sensor if it fails to detect fluid.
Red Seal field insights
These sensors often fail because of "oil in coolant" contamination coating the probe. If the probe is slimy, clean it with brake cleaner before replacing.
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