My cruise control on my 2007 gmc yukon shuts itself off while engaged

What is model year? Do the brake lites work? If not, I don't think the cruise will work either.

Can you check for applicable trouble codes? Some of the national brand auto stores will check codes for free. Also, I'd have to check applicable fuses, the control button on steering column, the cruise wiring in the steering column. Cruise linkages, where applicable.

I can't look up wiring diagram w/o model year.

The most common problem is brake light switch, assuming all other items are ok.

by cruise control being PCM control have dealership code scan see what causing cruise control turn itself on.

no reason for working for one and not the other
maybe it is how he drives
left foot resting on the brake pedal will not allow the cc to work as it takes very little to make the cc sensor disengage the control

I's possibly a bad ground at your harness or your multifunction swith could be going bad. this is your main control for your wipers bright dims as well as cruise control.

Cruise controls can cease to engage if the clutch or brake light cruise switch are out of adjustment. If this happens, try placing you foot under the clutch pedal (if equipped) and lift up on it (toward you) and hold it while engaging the cruise. If it now works, it will likely cut out when you remove your foot from under the pedal. Check the brake pedal in an identical fashion. Adjusting the switch at the pedals can often solve he problem. Some vehicles (Honda, Acura, Ford, to name a few) have a plastic insert that mounts in the pedal arm which presses against the switch. These can become brittle and fracture into pieces. My Acura has little pieces of blue plastic on the floorboard around the brake pedal one afternoon and I noticed the cruise didn't work. It was the pieces of the insert that had come to pieces preventing the cruise from coming on. I replaced the insert and no more problem with the cruise.

Check the speed sensor. Look up the location at autozone .com or google. It is either near the tranny or at the passenger side wheel. The speed sensor is almost always connected to cruise control problems.

Check your cruise control fuse or relay. It will be in your owners manual. If fuse is good than the cruise itself may be faulty. Check continuity on cruise controler itself. If there is power, than the controller itself is bad and need to be replaced. If there is no power than it may be a faulty switch.

There are a few things that can cause it. One which may sound stupid is actually valid on a lot of cars - if you have a burned out brake light bulb, some cars will not allow the cruise to be set. Make sure all of your bulbs are working right.

You could also have a failure of the cruise control buttons. On my Audi, the cruise control is on a stalk on the column, and is known to overheat and fail. A search of the internet should reveal if this is a known issue on your model year Yukon. Search "cruise control failure Yukon" and see if something comes up - chances are there is information out there that will tell you if this is something that is typical of your vehicle.