SPN 110 - FMI 3 (Fault Code 144)

Engine Coolant Temperature 1 Sensor Circuit - Voltage Above Normal or Shorted to High Source

Engine Coolant Temperature Sensor Circuit

Fault Code: 144
PID(P), SID(S): P110
SPN: 110
FMI: 3/3
Lamp: Amber

REASON: High signal voltage or open circuit detected at engine coolant temperature circuit.

EFFECT: Fan will stay ON if controlled by the engine control module (ECM).

Circuit Description:
The coolant temperature sensor is a variable resistor sensor and is used to measure the temperature of the coolant of the engine. The engine control module (ECM) supplies 5 volts to the coolant temperature signal circuit. The ECM monitors the change in voltage caused by changes in the resistance of the sensor to determine the coolant temperature.

Component Location:
The engine coolant temperature sensor is located on the thermostat housing.

Conditions for Running the Diagnostics:
This diagnostic runs continuously when the keyswitch is in the ON position or when the engine is running.

Conditions for Setting the Fault Codes:
The Engine Control Module (ECM) detected the engine coolant temperature signal voltage was out of range high.

Action Taken When the Fault Code is Active:
• The ECM illuminates the amber CHECK ENGINE lamp and/or the malfunction indicator lamp (MIL) immediately when the diagnostic runs and fails.
• A default value is used for the engine coolant temperature reading.

Conditions for Clearing the Fault Code:
• To validate the repair, perform a key cycle, start the engine and let it idle for 1 minute.
• The fault code status displayed by the recommended Cummins® electronic service tool or equivalent will change to INACTIVE immediately after the diagnostic runs and passes.
• The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
• The "Reset All Faults" command in the recommended Cummins® electronic service tool or equivalent can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.

Shop Talk:
The engine coolant temperature sensor shares return wires in the engine harness with other sensors. An open return can cause multiple fault codes to be active. Before troubleshooting Fault Code 144, check for multiple fault codes.
Possible causes of this fault code include:
• Open return circuit in the harness, connectors, or sensor.
• Open signal circuit or shorted to a voltage source.
• Malfunctioning engine coolant temperature sensor.

Read More:
SPN 91 - FMI 1 (Fault Code 147)
SPN 110 - FMI 4 (Fault Code 145)


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