Scan Tool Data Definitions

WARNING: This page is about a different car, the 2004 Chevrolet Monte Carlo and 2004 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.

ECT Sensor: The scan tool displays -40°C to +151°C (-40°F to +304°F). The Engine Coolant Temperature (ECT) sensor is mounted in the coolant stream. The 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 the PCM monitors a high signal voltage and interprets it as a cold engine. As the sensor warms the voltage signal decreases and the PCM interprets the lower voltage as a warm engine.
FC Relay 1 Command: The scan tool displays On or Off. The PCM is commanding Fan Control relay 1 On when the scan tool indicates On. When the PCM commands the Fan Control relay 1 On, both fans are enabled on low speed.
FC Relay 2 and 3 Command: The scan tool displays On or Off. The PCM is commanding all 3 fan control relays on when the scan tool indicates On. When all fan control relays are activated, both cooling fans are enabled on high speed.
FC Relay 1 Circuit Status: The scan tool displays OK, Fault, or Invalid State. This parameter indicates the state of the driver circuit for this device.
FC Relay 2 and 3 Circuit Status: The scan tool displays OK, Fault, or Invalid State. This parameter indicates the state of the driver circuit for this device.