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

Under the Rear of the Vehicle, Near the Rear Suspension Carrier


Object Number: 525002  Size: LF
(1)Automatic Level Control Compressor
Figure 2:

Left Front of the Vehicle, Near the Strut


Object Number: 525004  Size: LF
(1)Suspension Position Sensor -- LR, RR Similar