2002 Yukon xl 5.3 1500 brake lights

A couple days ago both brake lights stopped
working I figured it was the stop light switch since
when I turn my lights on the rear lights work.
Replaced the stop light switch and still don't work.
But I noticed when I jiggle the plug for the stop
light switch it makes a clicking noise what sounds
like a relay underneath my steering wheel. But still
no brake lights and the rear lights still work when I
turn my lights on????