how do i change the wiring harness in my 2002 chevy express van conversion on 2002 Chevrolet Express 1500

when my lights are off the brake lights turn on,but when i turn my park or headlights on my brake lights dont turn on when i press on the brakes bought new tail light harness need to no how to install them on a van conversion.hope this solve the brake light issues.

1 answer
Problem is the ground circuit in the bulb sockets! Replace them.