Can't control temperature

Occasionally I cannot reduce the temperature of the heat/air conditioning. If I turn the temperature knob to full hot to warm the interior of the Tahoe and later turn the knob to a cooler setting, it continues to blow full hot air (even if the temperature knob is on the full cold setting). If you stop the vehicle and turn off the ignition, it will reset it sometimes. It is a 2001 Tahoe with standard air conditioning. Any help?

Your temperature control actuator is bad. It's a little motor that moves the temp door. They are about $70 at the dealer. To change it you need to remove the knee trim panel on the passenger side (3 screws, 7mm socket). The actuator is in the center above the transmission hump. It has one harness plugged into it and 2 screws (5.5 mm). Take the screws out and it should drop straight down. Align the actuator with the lever on the door and put the screws in. Plug the harness back in. Turn your temp control to cold and remove the HVAC 1 fuse. Should be in the fuse panel on the drivers side of the dash. Turn your key to run and leave it on for at least 1 minute. Turn your key back off and put the fuse back in.
P.S. The trim panel is a PITA to get off, so while you have it off check to see if you have the cabin air filters and change them while you are under there.

Your 01 is the same as my 04