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

Ignition 3 and Accessory Voltage


Object Number: 2075728  Size: FS
Figure 2:

Ignition 2/3 Voltage


Object Number: 2155214  Size: FS
Figure 3:

Ignition 1 Voltage


Object Number: 2075730  Size: FS