no brake lights, changed bulbs, cked fuses, replaced pressure switch. on 2002 Chevrolet Trailblazer

is there a relay along with fuses for the brake light and if so where and what amp ?

Check for voltage going 'to' the brake light switch first. If ok check for voltage comming 'from' the switch. If that is ok, suspect the cluster/signal light/ switch......If no voltage at the brk light switch,, you missed the open fuse, check them with a test light!! If you are not equiped to do these tests..take it in to the shop for these tests and repair!