have no tail lights .brake lights work when headlights are off .trun single lite up. when you push brake they flash faster .
On GM vehicles this is usually a blown fuse....on GM the insturment cluster lights also go out..
I had the same issue. Brake lights, turn signals, back up lights all worked. The tail lights didn't. Never found out why... I pulled out the headlight switch out and spliced in to the brown wire on the switch and the brown on driver side tail light. After that the other tail light worked and tag lights too
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