SPN 110 - FMI 4 (Fault Code 145)

SPN 110 - FMI 4 (Fault Code: 145)
ISB, ISC, and ISL - Engine Coolant Temperature 1 Sensor Circuit

Fault Code: 145
PID(P), SID(S): P110
SPN: 110
FMI: 4/4

REASON: Engine Coolant Temperature 1 Sensor Circuit - Voltage Below Normal or Shorted to Low Source. Low signal voltage detected at engine coolant temperature circuit.

EFFECT: Possible white smoke. Fan will stay ON if controlled by ECM. No engine protection for engine coolant temperature.

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 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.

The engine coolant temperature value is used by the ECM for the engine protection system and engine emissions control.

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.

Conditions for Setting the Fault Codes:
The ECM detects that the coolant temperature signal voltage is less than 0.12-VDC for more than 1 second.

Action Taken When the Fault Code is Active:
• The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
• A default value is used for the coolant temperature reading.

Conditions for Clearing the Fault Code:
The ECM will turn off the amber CHECK ENGINE light immediately after the diagnostic runs and passes.

Shop Talk:

  • Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe® Online for applicable fixes to the calibration stored in the ECM. If necessary, recalibrate the ECM.
  • The engine coolant temperature sensor shares return wires in the engine harness with other sensors. A shorted return can cause multiple fault codes to be active. Before troubleshooting Fault Code 145, check for multiple fault codes.

Possible causes of this fault code include:
• Signal shorted to ground in the harness
• Signal shorted to return or ground in the sensor.

Read More:
SPN 110 - FMI 3 (Fault Code 144)
SPN 100 - FMI 4 (Fault Code 143)


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