CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – FAULT CODE 145

Engine Coolant Temperature 1 Sensor Circuit – Voltage Below Normal or Shorted to Low Source


Overview

CODE REASON EFFECT
Fault Code: 145
PID: P110
SPN: 110
FMI: 4/4
LAMP: Amber
SRT: 

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

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

ISX – Engine Coolant Temperature 1 Sensor Circuit
SMALL | MEDIUM | LARGE
ISM – Engine Coolant Temperature 1 Sensor Circuit
SMALL | MEDIUM | LARGE

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. Refer to Procedure 100-002 (Engine Diagrams) in Section E for a detailed component location view.

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. Refer to Procedure 019-032 (ECM Calibration Code) in Section 19 in the corresponding Troubleshooting and Repair Manual for the engine being serviced.

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.

Refer to Troubleshooting Fault Code t05-145

Last Modified:  09-Jul-2010