I have a 2008 GMC Sierra 1500. The cruise control was intermittent and finally stopped working. I read the forum about the brake light switch, so I replaced it today. Didn't change the problem. Checked the fuses and they're all good. But, I don't have brake lights if the ignition is off. They only work if the key is turned on. Is that a defective brake light switch or some other problem?

 

did you use an OEM switch? Next thing would be checking for codes