Powertrain Controls - ECM/PCM

Diagnostic Chart.:

Coolant Temperature Sensor (CTS) Wiring.:

Coolant Sensor And Intake Air Sensor Resistance Chart.:

DESCRIPTION


The coolant temperature sensor (CTS) is a thermistor located in a coolant passage of the engine's cylinder head. When coolant temperature is cold the sensor has a high resistance, as temperature increases the resistance of the sensor decreases. The PCM provides a five volt signal to the coolant sensor, which is also connected to PCM ground. The PCM reads the voltage drop on the signal line to determine coolant temperature.

CODE PARAMETERS

Code 14 will set if:


^ The CTS reads over 140°C (284°F).


^ The engine has been running over 10 seconds.

DIAGNOSTIC AIDS

^ Refer to Temperature vs. Resistance Chart.


^ When attempting to diagnose an intermittent problem, use the Scan Tool to review supplemental diagnostic information. The supplemental data can be used to duplicate a problem. Select MALF History from Scan Tool EC menu.


^ Check the tightness of the female terminal grip with a spare male terminal.


^ Start engine and observe CTS reading on Scan Tool. Normal operation is for the CTS to rise smoothly to approx. 85°C (190°F) (thermostat opens). The CTS should then stabilize.


^ The PCM will turn the coolant fan On if a Code 14 is set.


^ Code 14 can be set if there is a problem with the engine cooling system.


^ CTS may be compared to ATS temperature with Scan Tool if engine has cooled overnight at ambient temperature. They should be within four degrees of each other with ignition On and engine Off.