The HVAC Scan Tool Data Definitions contains a brief description of all HVAC related parameters available on the scan tool. The list is in alphabetical order. A given parameter may appear in any one of the data lists. In some cases, the parameter may appear more than once or in more than one data list in order to group certain related parameters together.

PCM -- Engine Data 2 -- A/C Clutch Feedback Sig: The scan tool displays Relay On or Relay Off. Relay On is displayed when the PCM has energized the A/C compressor clutch relay.

PCM -- Engine Data 2 -- A/C Compressor Cycling: The A/C compressor Cycling Switch opens when the low side pressure limit is reached. The PCM monitors the state of this switch and cycles the compressor to prevent evaporator freeze up.

PCM -- Engine Data 2 -- A/C Relay Command: The scan tool displays On or Off. On is displayed when the PCM has energized the A/C clutch relay.

PCM -- Engine Data 2 -- A/C Request Signal: The scan tool displays Yes or No. The PCM uses the A/C request signal in order to determine if A/C compressor operation is being requested by the HVAC control module.

PCM -- Engine Data 2 --A/C Sec. High Pressure: The secondary high pressure switch closes when the A/C systems high pressure limit is approached. The VCM monitors the state of this switch for compressor and auto recirculation operation. The switch closes at a high pressure value which is calibrated for specific platforms. The VCM continuously monitors the secondary high pressure switch when A/C has been selected by the operator.

PCM -- Output Controls -- A/C Relay: The scan tool displays On or Off, you can use this feature to cycle the compressor clutch any time the ignition is in the On position.