Originally Posted by eljefino
The seat belt relay, for the door-mounted 3-point belts, was to disable the inertia reel so you could whip the door open quickly, unspooling a lot of belt, while leaving the NHTSA-required "passive" belt buckled in its "emergency release."
This broke in my 1992 cutlass ciera, and the "Fasten Seat Belt" dash light came on, differently, to indicate some sort of code (?)
I unplugged the dumb relay, leaving the inertia reel always available, and unbuckled the belts manually like everybody else.
Glad OP found his issue.
Lucky you, actually getting an indication. I didn't -- and proceeded to basically get only 2 years or so out of my batteries, constantly needing to charge them even in the middle of the summer. And a few incidents of the battery going dead in airport parking lots, requiring a boost to get back home.
Once I finally tracked down that issue and pulled the relay, magically my battery seems to be lasting properly now. But between 2005 and 2015...what a nightmare! I even removed the negative battery cable so many times and re-attached it that I stripped out the negative battery terminal, and suffered a total electrical blackout one time. (all the money saved from not changing the oil in 100k miles except once to deal with a LIM issue and the flush thereafter....went into replacement batteries, boosts, etc., though Costco's 3-year full replacement warranty was generous and abusable, albeit embarrassing given my profession!).
Those seat belts...yeah very stupid. I tried using them "as intended" once....