GM-GMC: no brake lights

Question
Working on a 1998 chevy 1/2 ton 4x4,have 3rd brake light but rear brake lights don`t work.Been through harness all is good, replaced all fuses and brake lite switch,relay under hood also bulbs are good. there is a white wire in the harness that lites with the pedal but goes nowhere

Answer
i would venture to guess its the same issue i had with a 99 suburban, the brake light plates the actual plate that the lights plug into. tail light circuit board.

https://www.google.com/search?q=tail+light+connector+plate+1998+chevy+truck&oq=tail+light+connector+plate+1998+chevy+truck&aqs=chrome..69i57.13087j0j4&sourceid=chrome&es_sm=0&ie=UTF-8#q=tail+light+connector+plate+1998+chevy+truck&tbm=shop

mine had three connectors but yours will look similar to the one in the link.

this was a known issue with gm trucks, i found this out after i rewired the entire back end of my truck
all the way to the black circuit box under the rear next to the driver tire. check that too but my guess is that's not it.

hope this helps