Scan Tool Data Definitions

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

PCM - Engine Data 2 - A/C Clutch Feedback Signal: The scan tool displays Engaged or Disengaged. Represents the state of the A/C compressor clutch as seen by the PCM via the A/C compressor clutch feedback circuit.

PCM - Engine Data 2 - A/C High Side Pressure: The scan tool displays -103 to +3119 kPa, -14 to +452 psi. This parameter represents the A/C refrigerant pressure sensor voltage signal converted to pressure.

PCM - Engine Data 2 - A/C High Side Pressure: The scan tool displays 0 to 5 volts. The output of the A/C refrigerant pressure sensor.

PCM - Engine Data 2 - A/C Off For WOT: The scan tool displays Yes or No. Yes indicates that the PCM has disabled the A/C compressor because the TP sensor signal is at wide open throttle.

PCM - Engine Data 2 - A/C Pressure Disable: The scan tool displays Yes or No. Yes is displayed when the system pressure exceeds 2968 kPa (430 psi).

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 assembly.

PCM - Output Driver Data - A/C Relay Circuit Status: The scan tool displays OK or Fault. Fault is displayed when an open or short is detected in the A/C compressor clutch relay ground circuit.

PCM-ECT: The scan tool displays a range of -40 to +151°C (-40 to +304°F). The powertrain control module (PCM) applies 5.0 volts to the ECT sensor circuit. The sensor is a thermistor which changes internal resistance as the engine temperature changes. When the sensor is cold, internal resistance is high, the PCM senses 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.