Just wanted to make this post in case other GMT800 owners have the same problem I did. I did a lot of internet searching and never found the problem described exactly like the issue I was having, so hopefully this post helps someone.

I changed all of the taillights (right, left, and cab-mounted) on my 2005 Silverado to LEDs. After I did, the cruise control started acting up. When the ambient temperature was warm (above 50 degrees F), it worked fine. If it got a little cooler (between 30F and 50F), it would do weird things like turn off randomly and turn off when I turned on the windshield wipers. Below 30F, I basically had no cruise control. It would sometimes come on, but never stay on; but usually just not come on at all. I am paralyzed and use a wheelchair, so I drive with hand controls. It was getting really old holding the gas pedal down on my 5-6 hour drives when it was cold, so I did a lot of research and testing. Brake light switch under the dash was just fine. Electricity has less resistance when it's cold, and LED lights have less resistance than the standard bulbs on our trucks. So when it got cold, the LED brake lights simply didn't have enough resistance to tell the cruise control that the brake lights weren't on - hence that the brake pedal wasn't being pushed. I installed resistors (Amazon link: ) in the wiring for the brake lights (one resistor on each side) and this has completely fixed my cruise control. Cheap fix, just needed to fab and install a couple of small metal brackets (the resistors give off heat, so you don't want to mount them to the plastic taillights). Again, hope this helps.