GM Service Manual Online
For 1990-2009 cars only
ECT Sensor: The scan tool displays -40 to +151°C (-40 to +304°F). The engine coolant temperature (ECT) sensor is mounted in the coolant stream. The powertrain control module (PCM) applies 5 volts to the ECT sensor circuit. The sensor is a thermistor which changes internal resistance as temperature changes. When the sensor is cold (internal resistance high), the PCM monitors a high signal voltage and interprets it as a cold engine. As the sensor warms (internal resistance decreases), the voltage signal decreases and the PCM interprets the lower voltage as a warm engine.

FC Relay 1 Circuit Status: The scan tool displays OK, Fault, or Invalid State. These parameters describe the condition of the control circuit.

FC Relay 1 Command: The scan tool displays ON or OFF. This represents the PCM commanded state of both fans.

FC Relay 2 and 3 Circuit Status: The scan tool displays OK, Fault, or Invalid State. These parameters describe the condition of the control circuit.

FC Relay 2 and 3 Command: The scan tool displays ON or OFF. This represents the PCM commanded state of both fans.