You can test the cruise lever before replacing. There's a small edge style connector clipped under the dash with only 4 contacts on it. 1 is ground and it may take some experimenting to figure out which is which as the wire colors are hidden in a black outer insulation jacket. Unplug it and get your multimeter set on continuity. When you figure out which one is ground, you can test on the other contacts and actuate the switches to see if any of them aren't working.
The most common failure are the wires at the bend as Schurkey has pictured. Also, I have revived a few of them by spraying contact cleaner into the switch area and repeatedly working the switches until they began functioning again. My favorite cleaner for this is DeOxit.
The brake switch is suspect as well. You can test the brake switch easily with the multimeter as well. It's simply 3 sets of contacts. It's also easy to pop the cover off it and see if any of the leafs inside look broken or weak. The brake switch is cheap to replace.
The brake switch can also be out of adjustment on the 1988-1993 trucks (1994-up are not adjustable.) Procedure quoted from Chevytalk member Chevytech:
Brake Switch adjustment
Here is how the switch is adjusted on 1988-1993 C/K trucks:
On the curved side of the switch, which is pointing down and somewhat towards the front of the vehicle when installed, the end of a lever protrudes slightly out of a slot.
While holding the brake pedal down a little ways, slide the lever that protrudes from the slot toward the driver’s seat.
Let go of the lever, then return the brake pedal to its fully released position, and the switch should self adjust. Make sure the pedal returns all the way and is not held partially applied by the switch not adjusting.
Finally to your other questions - the ABS module being disconnected has no affect on the cruise control. And, there is no LED or light bulb indicator on the GMT400 trucks for the cruise being on or engaged.
Richard
