Brake lights

First check the ground to the tail lights, do this remove a tail light bulb and socket, you can see a bit of the brass bulb base sticking out of the socket, use a jumper wire connect one end to a good ground then touch the other end to the bulb base. If the problem goes away repair or replace the ground wire. The less likely problem would be a tail light wire shorted into the brake light wire. I hope this helps.

I have an 03 Chevy Tahoe I changed the brake light switch, under the brake changed bulbs and check the fuses which wasn't blowed and brakes still want come on. Any help please