Powertrain Controls - ECM/PCM

Diagnostic Chart:

Circuit Schematic:

Temperature - Resistance Chart For Sensors:

ENGINE COOLANT TEMPERATURE CIRCUIT - TEMPERATURE OUT OF RANGE HIGH
The engine coolant temperature sensor is a thermistor located in the lower 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.

DTC PARAMETERS

DTC 14 will set if:
^ The ECT reads over 140°C (284°F).
^ The engine has been running over 10 seconds.

DIAGNOSTIC AIDS
Refer to Resistance Chart.

When attempting to diagnose an intermittent problem, use the Scan tool[1] to review supplemental diagnostic information. The supplemental data can be used to duplicate a problem.

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

Start engine and observe ECT reading on Scan tool. Normal operation is for the ECT to rise smoothly to approximately 88°C (190°F), as thermostat opens then stabilizes.

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

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

ECT may be compared to IAT 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.

Engine cooling fan also comes on if ECT exceeds 106°C.

[1]Select Malfunction History from Scan tool Engine Control (EC) menu.