Could be either a hard fault (a real component failure) or a bad connection.
Did you happen to pound on the steering wheel or slam the door? Either way to pull the trouble code or reset the light you need a tester. Give me a call tomorrow and we can discuss this further. 1-516-801-8201.
I believe that we saw this problem when I was performing your install at Pocono. You had a fuse in the passenger footwell that had been modified for some other equipment ( radio or alarm ). It wasn't wired together in the best way. Perhaps this connection came loose again and is the issue.
My airbag dash light has been on for a long time now as well. Dealer tells me they need to replace the passenger door airbag. I've got no reason not to believe them, but would love to find out it's just a fuse or something. Please share your findings....