2000 neon cruise control doesn't work

My gf recently got a 2000 neon. the cruise control didnt work before she got it. The dealer said they replaced the servo and it didnt help and they maybe it is the pcm. when the cruise on/off switch is pressed the cruise comes on the off after a split. When i disconnect the speed control? connetion from the brake pedal the on/'off switch works no problem. Is this my problem and all i need to do is replace this or how would i go about testing the pcm? If it is the speed control? on the brake pedal where can i get one? all i can seem to find is the whole cruise control kit. Thanks for any help in advacne.

the cruise control on my other neon still works, if it's possible for you we can negotiate a sale or something.

what did you have in mind?

I figured out what the part was called. The stoplight switch. $26 at the dealer and $13 at autozone. I will pick this up and see if it works unless andyone has any tips.

just to update on this. I started messing with this again. I got a servo from pull a part and now the i can command the cruise on and off and can even set the cruise but now it will go off after maybe 10 seconds after turning the cruise control on, getting better i guess. I checked vacuum and it seems good. any ideas? Brake switch seems good as well.

edit: previously the cruise light would go on and then off right away and couldnt do anything
now i can turn the cruise on/off and it will stay on. When I set the speed it stay on for about 5/10 seconds then shut both the set and cruise light off disabling the cc until I shut off the car and restart it.

Fix update: Found a few broken wires that run along the front bottom of the car in the wiring harness (something tore it open). Fixed the wires and cruise control now works like a charm.