I have just followed your posts from the beginning. I bought a 99 430 2 months ago. found out today that my car has 100% exactly the same problem as yours - no CEL, no seatbelt light on ignition position #2.
worried, confused ???
Still working on it. I have been prepping my race car for a 3 day event on Aug 5-7.
Brakes, radiator, new fuel cell and some new suspension tricks.
Should have it posted by the end of Weds/Thurs.
Cheers,
Rob