Do you have normal or Xeon headlights? I don't want to state the obvious, but have you checked the fuse? They're fused for each light on these models.

 

Mike, looking at the diagrams for your vehicle, it can only be 1 of 3 things. You have a fuse, some wiring, and the headlight assembly itself. So, I would first try swapping the headlight fuses between the sides (ie, switch fuses F8 and F9 in the front distribution box, also do a quick visual inspection of the fuses, replace if questionable). If the problem switches sides, you know it is a bad fuse, replace the fuse on the side that is now blinking.

At this point, you need to do some work and see if you can spot anything wrong with the plug for the headlight assembly. If not, then odds are, you are looking at a bad headlight bulb/ballast (aka, ignitor). Now, the bulb is for halogen headlights and the ballast is for HID lights. I'm not sure what you have in your vehicle. If you need me to get more technical with this, let me know what you have and I can give some more instructions. If this doesn't fix the issue, then you have a wiring problem and about the only way that you will fix it is to run a new wire from the fuse box to the headlight assembly that is flashing. Again, if you need help, let me know.

 

Have you set it to auto mode, maybe?