My 2001 D2, had a small leak on my rear skylight from one corner. I checked the drain tube from blowing air up (located behind tail light). All clear. Still leaked. Tightened the bolts a bit on the sunroof glass. Still leaked. Removed the trim around the skylight to gain access to the headliner and underside of skylight. Tightened the skylight frame bolts. Aha, found three that were a bit loose. Skylight no longer leaks.

From reading many threads on this subject, the usual method was to remove the headliner. By using a stubby Torx-15 on a 1/4" ratchet you are able to gain the clearance needed without the need to remove the headliner. Placing a small LED flashlight between the headliner and roof also helps to find the screws. Sometimes, doing the smaller easier things first, pays off.

I would have to thank Brtipart's online how-to guide on fixing skylights.

 

Thanks for this, it rained here in AZ last night, so I covered mine with a moving blanket and blue tarp, just to be on the safe side. PO said they didn't leak, she was right.