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

Horns


Object Number: 354766  Size: LF
(1)Fender, LF
(2)Horn, LH
(3)Insulator
(4)Horn, RH
(5)Fender, RF
Figure 2:

HORN Relay


Object Number: 688142  Size: LF
Figure 3:

SRS Steering Wheel Inflator Module/Horn Pad


Object Number: 681636  Size: LF
(1)SRS Steering Wheel Inflator Module/Horn Pad
(2)Horn Switch Wires
(3)Horn Switch