Dealer tried to say it was because the passenger wasn't heavy enough , even though the light stayed on when no one was in the seat. Had to take it to 3 dealer and GM would not cover problem under warranty

In July of 08 I was involved in a front end collision. The seat belt did not lock when I went forward and as a result I injured my shoulder. When I mentioned this to the body shop they told me that the seat belts dont lock unless the air bags are deployed. I know it is ridiculous because when I get in the car and try to buckle up if I pull the seat belt out too fast it locks on me and I have to let it go all the way back in before I can get it to buckle.