Wiring? Taillights?

I would check the headlight switch itself. On the back will be one terminal for just parking lights. THis will either also include the instrument illumination wiring too, or it will be separate like on Foxes and SN's (I have not seen a four eye headlight switch). That is where I would start though. Your headlights work since that is a different position on the switch.

Good luck.

You can look at the schematics in the back of your repair manual or at the schematics on AZ's website.

I would remove the switch and backprobe the wires. You should see a constant feed to the switch and then with probing and a schematic, be able to see which wires do what. You will find one that is hot with the headlight switch all the way on (your headlights will be on). At that point, there should be one wire which does not appear to do anything and reads nothing or open. That wire's color should match the parking light wire color.

Now if you have juice to that point, you need to trace the parking light further. It should not be much further at all since the wire branches out into different directions. If one of those branches is bad, the other branches would work and provide other parking lights with light (unless your bad wire shorts to ground, which takes out the entire circuit).

Good luck.