Hey guys, on my way home from work I noticed my left turn signal rapidly flashing. Then discovered my drivers rear turn/brake was out. I have JW Speakers. I swapped my right and left lights and it still didnt work. Then put my stock taillight in, still nothing. I used my flashcal to check for codes and it pulled Code B1643 “rear left turn lamp control circuit low”. I checked all the wires that were visible, everything appeared to be ok, unhooked my trailer harness and bypassed it, still nothing. So its definitely not the taillight, bulb, or trailer harness, and apparently the turn signals don’t use fuses. Where should I go from here? Thanks!

 

The socket for the bulb should have four contacts in it. The two outer contacts are for the stop/turn filament.
Check for power at one of the outer contacts when the brake lights are on.
Check the other outer contact for continuity to ground with the brake lights off.