For 1990-2009 cars
ECT: 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 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 internal resistance high. The powertrain control module (PCM) monitors a high signal voltage and interprets it as a cold engine. As the sensor warms, the 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 or Fault. This parameter indicates the state of the driver circuit for this device.
FC Relay 1 Command: The scan tool displays OK or Fault. This parameter indicates the state of the driver circuit for this device.
FC Relay 2 and 3 Circuit Status: The scan tool displays OK or Fault. This parameter indicates the state of the driver circuit for this device.
FC Relay 2 and 3 Command: The scan tool displays On or Off. This parameter indicates the state of the high speed fan relay driver.
High Coolant Temp Lamp: The scan tool displays On/Off. The requested state of the engine coolant temperature indicator as commanded by the PCM. The body control module (BCM) receives a class 2 message from the PCM requesting illumination.
Low Coolant Lamp: The scan tool displays On/Off. The requested state of the low engine coolant indicator as commanded by the BCM.
Low Coolant Level: The scan tool displays OK/Low. This parameter indicates when the engine coolant level is low. The scan tool displays Low when the BCM detects the engine coolant level switch is closed.