Driver side rear turn signal is not working, I have replaced the bulb and checked fuses. What else could I check to get this fixed? All other signals and break lights are working perfectly.

 

Sometimes a simple light problem can get a little complicated especially if a Body control Module is involved..

Aside from that what might help would be to start working either from the signal light switch out to the lamp in the rear or working back from the lamp with the lamp requested on and checking for the break possibly in the wire from the switch to the lamp with either a test light or voltmeter.

 

Could be as simple as rust in the socket.

 

Do you have brake lights? I echo the thought of a bad socket. I had the same issue recently up front with turn signal and park light inoperative.