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

Instrument Panel Components, Left Side


Object Number: 689885  Size: MF
(1)Air Suspension Dump Switch
(2)PTO Switch
(3)Instrument Panel
Figure 2:

Inside of Frame Rail, Right Rear


Object Number: 690257  Size: MF
(1)Air Suspension Relief Valve
(2)Right Frame Rail