Use the Scan Tool Data Display Values and Definitions Information in order to assist in diagnosing the body control module (BCM) 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.
BCM-HVAC Data-A/C Switch: The scan tool displays On or Off. The body control module (BCM) uses the A/C Switch Input in order to determine if A/C compressor operation is being requested by the HVAC control module.ECM-A/C Relay Command: The scan tool displays On or Off. On is displayed when the engine control module (ECM) has energized the A/C clutch relay.
ECM-A/C Refrigerant Pressure: The scan tool displays 0 to 4000 kPa (0 to 580 psi). This parameter represents the A/C refrigerant pressure sensor voltage signal converted to pressure.
ECM-A/C Refrigerant Pressure: The scan tool displays 0 to 5 volts. The output of the A/C refrigerant pressure sensor.
ECM-A/C Request: The scan tool displays Yes or No. Yes is displayed when the BCM is requesting A/C system operation.
ECM-ECT: The scan tool displays a range of 40 to 151°C (40 to 304°F). The ECM applies 5-volts to the engine coolant temperature (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 ECM 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 ECM interprets the lower voltage as a warm engine.
