it would seem that you have a problem with the ground or the connector for the left side directional. it could be the front or the rear. the first thing to do is to check the sockets that the bulbs plug into for corrosion or for loose terminals. More often than not the problems like this are loose connections. turn the directionals on and wiggle the wires on the front and rear bulb sockets to see if they start working.you can check the grounds as well. the grounds are where the black wires from the sockets are bolted to the frame of the car. The ground for the left rear lights is inside the trunk on the left side under the panel that runs parallel to the rear bumper. It is a cap screw that holds several wires to the body. The left front should be grounded inside the left front fender; usually behind the battery or air filter housing depending on the layout of the engine compartment.the only other thing in common is the combination/turn signal switch on the column and that is a real possibility if the grounds and the connections are okay. that is not something you can do by yourself as it involves removing the airbag and the upper steering column. I'm afraid that's what you're going to find is the problem if the other things check okay.it is not a fuse problem; it is not a bulb problem; it is not a flasher problem.hope that helps