GM Service Manual Online
For 1990-2009 cars only
Figure 1:

Under Left Middle of Vehicle


Object Number: 1232745  Size: LF
(1)Automatic Level Control (ALC) Inflator Air Switch
(2)Automatic Level Control (ALC) Inflator Soleniod
(3)Automatic Level Control (ALC) Compressor
(4)Compressor Mounting Bracket
(5)Automatic Level Control (ALC) Compressor Relay
Figure 2:

Under Left Rear of Vehicle


Object Number: 772910  Size: LF
(1)Auto Level Control (ALC) Sensor