Do you have 3rd brake light & if so does it work? On a 95, not sure if it applies to all with 3rd brake light,
power from brake light s/w goes to flasher to turn signal s/w to rear lights...may be either a bad flasher or turn signal s/w.
@ brake light s/w power wire PK/DB,flasher WT/TN,pcm ground sense circuit WT/PK, ground BK. Fuse #3 15A brake light,fuse #4 15A turn sig flasher,fuse #5 20A hazard flasher. This is from a 95 service manual.
From a 90 service manual brake light s/w wires,power PK/BK,to column LB/BK @ column wt to turn/hazard s/w
from turn/hazard s/w @ column connection YL to GY/BK : left rear lights
DG to BR : right lights
above parking brake handle is a body harness connector, pin #7 left rear,pin #5 right rear lights.Check for loose connector,& check the turn signal s/w.