Automatic Level Control Scan Tool Data Definitions:

WARNING: This page is about a different car, the 2007 Cadillac SRX. However, it is still accessible from the selected car via links, so may be relevant.

The Automatic Level Control (ALC) Scan Tool Data Definitions contains a brief description of all scan tool parameters.

ALC Compressor: The scan tool displays Inactive/Active. The scan tool will display Active when the vehicle trim height is below a preset value. The ALC Compressor inflates the rear airlift shocks until the vehicle reaches the desired trim height. When the vehicle is at the desired trim height, the scan tool will display Inactive.
ALC Exhaust Solenoid: The scan tool displays Inactive/Active. The scan tool will display Active when the vehicle trim height is above a preset value. The ALC Exhaust Solenoid deflates the rear airlift shocks until the vehicle reaches the desired trim height. When the vehicle is at the desired trim height, the scan tool will display Inactive.
Battery Voltage Signal: The scan tool displays 0-26.0 volts. The battery voltage represents the system voltage measured at the controller battery input.
DSP Software Version: The scan tool displays the controller DSP software version number for service identification.
EEPROM Calibration ID: The scan tool displays the controller EEPROM calibration ID number for service identification.
GM Part Number: The scan tool displays the controller part number for service identification.
GMSCM Software Version: The scan tool displays the controller GMSCM software version number for service identification.