[ChevyTech]

You need to look closely at the terminals in the connectors to see if they are damaged or stretched out so they are not making connection.

The cruise has its own little harness going through the firewall so it does not go through the bulkhead connector or any thing else.

If it tests good on the inside, and bad on the outside, you need to move your way down the wire until you find the open/break.

The gray wire has a splice where it goes in two directions. One split goes to brake switch and the other goes out to the cruise module on the firewall.

My guess is once you find the problem with one of the wires , the other wires will have a problem in the same place. I would trace down the gray wire.

If you are testing the switch with an ohm meter and not a test light, it may test ok with a meter but can't handle any load and won't test good with the load of a test light.

You have identified a problem and are getting close. Don't give up now.