For 1990-2009 cars
AC Relay Command: This parameter indicates the commanded state of the A/C clutch control (MG) relay. The A/C clutch should be engaged when the scan tool displays on.
AC Request Signal: This parameter indicates whether the A/C switch on the instrument panel (IP) has been selected.
ECT Sensor: The scan tool range is -40°C to +140°C (-40°F to +284°F). The engine coolant temperature (ECT) sensor is a thermistor which changes internal resistance as the temperature changes. When the sensor is cold, internal resistance high, the PCM monitors a high signal voltage and interprets the voltage 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.