Pontiac Vibe 2003 Cruise Control routinely shuts itself off after working for a while

I have a 2003 AWD Pontica Vibe, automatic transition, almost to 100,000 miles, the majority of which are from midwestern highway driving. Last summer on a long highway drive, the cruise control mysteriously shut itself off after maybe 2 hours, and wouldn’t hold speed again no matter how many times I tried to reset it. When I stopped for gas and tried it again after restarting the car, it worked fine for months. I figured it need a reboot and didn’t worry about it. But since November the same thing always happens: the cruise control works the first time you set it for anywhere from 20 minutes to an hour, and then it shuts itself off. Any attempts to reset it after that will hold speed for anywhere from 10 seconds to about a minute. The “cruise” light on the dashboard flickers at the moment the speed drops, but doesn’t remain off. I am definitely not touching the brake, and there is no correlation with road conditions or weather as far as I can tell. We took it to the dealer in December to check for electrical problems, but they didn’t find any error codes. I’m not sure what the next step is - should we drive it on the highway for an hour and THEN check the codes once it’s in a malfunctioning state? Or is there another likely culprit?

If you can check the codes near in time to a malfunction that would be good.

But the first thing I would check is the brake light switch. I don’t know the specific design on this car, but on many the switch itself is adjustable and can be triggered even if you don’t use the brake. A bigger reason to check it is that if it does need to be adjusted and is triggering your brake lights, then this produces a safety issue for you.

cigroller, I had assumed it was unlikely to be a brake light switch problem since I assume that would affect the performance of cruise control without affecting the indicator light for the cruise-control system. E.g. when the cruise control is properly functioning and I hit the brakes, speed drops but the “cruise” light on the dash does not flicker. Nevertheless, I suppose it’s worth checking, just in case!

+1 to Cig’s post.

The light is simply telling you that the cruise control system is enabled and ready to be engaged. Its illumination is not telling you that the CC is engaged.

The switch was the first thing that came to my mind too. In addition to lighting the brake lights, it also disengages the cruise control. These two circuits, however, go through different switch contacts, so it is entirely possible for the switch to have flakey contacts for the cruise control circuit and still be functioning properly for the brake lights.

I don’t have access to the circuitry, but I feel confident in suggesting that you have a relay in the cruise control circuitry as well, and that could be getting flakey. That relay will probably be in the relay box under the hood, but I remind you that I don’t have any wiring diagrams or schematics to reference, so I’m guessing here. You’ll need to do some research to check out my suggestions.

Thanks for some extra detail, mountainbike. I understand cig’s post better now, and the reasons for checking this stuff out. I’ll definitely look into the switch and relay. I’ve gotten so used to using cruise control that a 2 hour drive without it is really annoying, and a 6 hour drive is torture!

It could be failure in the cruise control stalk off the steering column.

circuitsmith, I’ll add it to the list, thanks