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

Instrument Panel Switches, Center Forward View


Object Number: 1400889  Size: LF
(1)Outside Heated Mirror Switch (DNN)
(2)High Idle Switch (UF3) or Power Take-Off (PTO) Switch
(3)Exhaust Brake Switch (K40)
(4)Rear Axle Driver Control Switch - Two Speed (HPZ and Automatic Transmission)
(5)Traction Control Switch (NW9)
(6)Overdrive (OD) Defeat Switch (Allison® LCT)
(7)Marker Lamp Switch (JE4, RQ2 and U86, or JE4 and RQ3)
Figure 2:

Front Chassis Harness to Brake Components


Object Number: 231739  Size: LF
(1)Brake Pressure Modulator Valve (BPMV), Right Side Front
(2)BPMV, Left Side Front
Figure 3:

Front Wheel Speed Sensor (WSS)


Object Number: 231740  Size: LF
(1)Wheel Speed Sensor (WSS) - RF (LF Similar)
Figure 4:

Chassis Harness Routing


Object Number: 1595416  Size: LF
(1)Hydromax Fuse (JE3)
(2)ABS Relay (JE4)
(3)Power Brake (P/B) Booster Pump Relay
(4)Surge Tank Bracket
(5)Cab Bridge
(6)C104 (Upfitter PTO Connector)
(7)C405 Front Chassis Harness to Rear Chassis Harness
(8)Trailer Stop Lamp Relay (RQ2 and U86 or RQ3)
(9)C2
(10)C1
(11)C3
(12)C411 Front Chassis Harness to Fuel Tank Harness
(13)C405 Front Chassis Harness to Rear Chassis Harness
(14)C403 Front Chassis Harness to Rear Chassis Harness
(15)C406 Front Chassis to Tractor/Trailer Harness
(16)C421 Front Chassis Harness to Air Compressor Harness (K16)
(17)Fuse Block 2
(18)Fuse Block 1
(19)C100 Front Chassis Harness to Upfitter AUX WRG Connector
(20)C106 Front Chassis Harness to Upfitter PTO Harness
Figure 5:

Electronic Brake Controls Harness and Components , LH View


Object Number: 231756  Size: LF
(1)RH Rear Wheel Speed Sensor (WSS) (JE4)
(2)RH Rear Gender Adapter Connector (4 male-to-male cavities) (JE4)
(3)RH Rear Brake Pressure Modulator Valve (BPMV) (JE4)
(4)LH Rear BPMV (JE4)
(5)LH Rear WSS (JE4)
(6)LH Rear Gender Adapter Connector (4 male-to-male cavities) (JE4)
Figure 6:

Rear of Frame, Right Rear View


Object Number: 231761  Size: MF
(1)Wheel Speed Sensor (WSS) -- LR (RF Symilar)