does brake light switch control brake lights in trailer harness?
 

04 z71 tahoe, The brake lights suddenly stopped working, all 3, left, right, center top. I checked all applicable fuses. Still good. I noticed if I plug a tester in the trailer harness, it indicated the connection for the harness brake lights is working. If all the other lights arent working, but the harness brake lights are working, could it still be the Brake Light Switch? Does the BLS control/affect the harness brake connections? TIA