The door switches provide a ground to both the courtesy lamps and the anti-theft alarm (ie they trigger the alarm.)

Does the anti-theft work at all? Try opening the hood with the vehicle locked - or just about anything else, apparently. The anti-theft wiring diagram covers at least 4 pages in the service manual. Do all the locks work? Try locking the car from the passenger side?

I'm generating these ideas from looking at the schematics...sorry I don't know the common problems, etc.

best & good luck,

Dave