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

Center of the I/P


Object Number: 826775  Size: LF
(1)Marker Lamp Switch (RQ2 and U86 or RQ3)
(2)Automatic Transmission Fluid Temperature (TFT) Gage (Allison® LCT/UTX)
(3)High Idle Switch (UF3)
(4)Air Brake Pressure Gage (JE4)
(5)Traction Control Switch (NW9)
(6)Outside Heated Mirror Switch (DB6/DB8)
(7)Exhaust Brake Switch (K40)
(8)Rear Axle Driver Control Switch - Two Speed (HPZ/Automatic Transmission)
(9)Inflatable Restraint I/P Module Disable Switch (AK5 w/o AQR)
(10)Air Suspension Dump Switch (G40/G45/GSJ)
(11)Power Take-Off (PTO) Switch
(12)Driver Information Center (DIC)
Figure 2:

Two Speed Rear Axle Harness, Left Rear View


Object Number: 690061  Size: SF
(1)Rear Axle Shift Relay -- Two Speed
Figure 3:

Rear Differential, Front View


Object Number: 690066  Size: SF
(1)Rear Axle Shift Motor -- Two Speed