GM Service Manual Online
For 1990-2009 cars only
AC Pressure Sensor: The scan tool displays 0-3450 kPa (0-500 psi). The voltage applied to the powertrain control module (PCM) input from the A/C refrigerant pressure sensor is converted to a pressure value.

A/C Relay Command: The scan tool displays On/Off. The scan tool displays the control decision for the compressor clutch relay output as determined by the PCM.

A/C Request: The scan tool displays Yes/No. Yes is displayed when the body control module (BCM) receives an input from the HVAC control assembly for an A/C request. No is displayed when there is no A/C request.

A/C Request Signal: The scan tool displays Yes/No. The scan tool displays Yes when the PCM receives a class 2 message from the body control module (BCM) to engage the A/C compressor clutch. The BCM receives a voltage input from the HVAC control assembly through the evaporator temperature sensor for an A/C request. The scan tool displays No when the PCM receives a class 2 message from the BCM to disengage the A/C compressor clutch.

ECT Sensor: The scan tool displays -39 to 140°C (-38 to 284°F) . The voltage applied to the PCM input from the engine coolant temperature sensor is converted to a temperature value.