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

Engine Coolant Level Switch -- 2500 Series


Object Number: 1463999  Size: FS
Master Electrical Component List
Cooling System Description and Operation
Control Module References
Fan Controls - Except L18
Power, Ground, DLC, and Splice Pack SP205
G104 and G107
Figure 2:

Fan Controls -- 1500 Series


Object Number: 1469394  Size: FS
Master Electrical Component List
Cooling System Description and Operation
Control Module References
Engine Coolant Level Switch - L18
B+ Bus - 1 of 2