Update on my AudioVox cruise.
I went through all the trouble-shooting guides. I checked all my voltages at the servo and everything was fine. The LED on the servo turned on when the cruise was turned on and blinked faster when the engine revved, so all OK. My trouble shooting guide said the LED should be continuously lit when either brake was applied. On mine the LED turned off (which seemed logical to me). I took the servo apart and checked for leaks etc, but found nothing wrong. I finally concluded that there must be a problem in the servo's circuit board.
Slow forward about a year. I finally bit the bullet and ordered a new servo from Murhp's. It got to me within about 3 days. I did an easy install. I only needed to take the old one out, bolt the new one in, plug the new one in and hook up the throttle cable ( I was wise enough to zip tie the throttle connector chain up, so I would not have to fish for it). Worked like a charm on the first test drive. That LED does not light continuously when the brakes are applied as stated in the trouble shooting guide that I have.
It seems others have had problems with the servo circuit board too. Consider that the likely culprit if all your other trouble-shooting turns up OK.