Detailed guide for SPN 111 FMI 4
Back to top ↑What SPN 111 FMI 4 means
SPN 111 identifies engine coolant level. FMI 4 indicates voltage below normal or a circuit shorted toward a low source.
Detroit documentation describes this fault as a coolant level circuit failed low condition and directs diagnosis toward the sensor circuit and possible short to ground.
What to check first
Inspect the coolant level sensor connector for bent, spread or corroded terminals. Examine the harness near the radiator, reservoir and chassis for chafing or damaged insulation.
Use the manufacturer's wiring diagram to test the coolant level circuit for a short to ground and verify circuit integrity.
Also confirm the actual coolant level because some applications can associate the circuit condition with a low-level state.
Before replacing the sensor
Do not replace the sensor without circuit testing. Wiring faults can produce the same FMI.
After repairs, clear the fault according to the OEM procedure and verify that the coolant-level signal is operating normally.
Mechanic community notes for SPN 111 FMI 4
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