Use the Scan Tool Data Display Values and Definitions Information in order to assist in diagnosing the HVAC control module problems. Compare the vehicles actual scan tool data with the typical data display value table information. Use the data information in order to aid in understanding the nature of the problem when the vehicle does not match with the typical data display values.
The scan tool data values were taken from a known good vehicle under the following conditions:
| • | The ignition switch is in the ON position. |
| • | The engine is running at idle. |
| • | The vehicle is in PARK. |
| • | The doors are closed. |
| • | The windows are closed. |
| • | The A/C is ON, in UPPER mode. |
| • | The ambient air temperatures are at 22-27°C (70-80°F). |
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 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 0.00-5.00 volts. This parameter represents the A/C refrigerant pressure sensor signal.
PCM-Engine Data 2--A/C Off for WOT: The scan tool displays Yes or No. Yes is displayed when the PCM de-energizes the A/C compressor clutch relay to reduce engine load during 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 w/LG8 (V6)-A/C Request Signal: The scan tool displays Yes or No. Yes is displayed when the HVAC Control Module is requesting A/C system operation.
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--3.1L
ECT Sensor: 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 volage signal 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.PCM--3.8L
ECT Sensor: 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 volage signal 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.