Circuit DescriptionThe 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.
The engine coolant temperature value is used by the ECM for the engine protection system and emissions control.
Component LocationThe engine coolant temperature sensor is located on the exhaust side of the engine near the thermostat housing.
Conditions for Running the DiagnosticsThis diagnostic runs continuously when the engine is operating.
Conditions for Setting the Fault CodesEngine coolant temperature has been below 60?C [140?F] for over 1 hour during a period of extended idle.
Action Taken When the Fault Code is ActiveThe ECM illuminates the amber CHECK ENGINE lamp immediately when the diagnostic runs and fails.
Conditions for Clearing the Fault CodeTo validate the repair using a Diagnostic Road Test, utilize a route that incorporates both stop-and-go city driving and steady state highway driving. It may be necessary to load the unit for certain diagnostics in the ECM to run.To validate the repair using a Chassis Dynamometer Test, utilize a routine that incorporates acceleration and motoring events, steady state highway operation, and load. This will simulate normal driving and allow the diagnostics in the ECM to run.The fault code status displayed by INSITE? electronic service tool will change to INACTIVE immediately after the diagnostic runs and passesThe ?Reset All Faults? command in INSITE? electronic service tool can be used to clear active and inactive faults.
Shop TalkIf this fault indicates that coolant temperature is below a calibratible limit set in the ECM.
Refer to Engine Coolant Temperature Below Normal troubleshooting symptom tree tree in Section TS.
Possible Cause:1) Coolant temperature Sensor failure2) ECM calibration