Cummins Fault Code
Free · no signupCummins 144 (SPN 110 FMI 4)
Fan stays on 100%; Gauge pinned to Hot; Hard starting in cold weather; Engine derate.
System
Not specified
Symptom
Fan stays on 100%; Gauge pinned to Hot; Hard starting in cold weather; Engine derate.
Diagnosis & fix steps
Engine Coolant Temperature 1 Sensor Circuit - Voltage Low.
LOGIC: Signal voltage < 0.5V (Short to Ground). The ECM interprets a dead short as an extremely high temperature or a circuit failure.
ACTION: 1. The "Unplug" Test: Unplug the sensor. If the code changes to 145 (FMI 3 - Voltage High), the wiring is healthy and the Sensor is shorted internally.
2. Harness Inspection: Check for rub-points on the harness near the thermostat housing or lifting brackets.
3. Reference Check: Verify 5.0V between Pin A and Pin B on the harness plug with the key ON.
FIX: Replace the Engine Coolant Temperature Sensor or repair the signal wire shorted to ground.
Red Seal field insights
This sensor is often located near the thermostat housing. If you've recently done a coolant flush or water pump, check the connector for trapped moisture or "Green Crusties" which can track voltage to ground.
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