I'd like to share an interesting Ford airbag warning light story. I work for a very large department, when at the peak of the Crown Victoria PI (2010 / 2011), we had over 1,200 of them.
The airbag warning lights would start coming on in these cars 2-3 years after they were issued. It ended up being the small airbag warning bulb right over the glove box was burned out. Basically, it was the bulb that lit up when it detected that no one was in the passenger seat and it indicated that the passenger side airbag was inactive due to no one sitting there. The guys work alone and the cars are ran many, many hours each day, so that little bulb would just stay lit. Once it burnt out, the main airbag light on the instrument cluster would illuminate. Kind of bothers you seeing that. I forgot what the error code actually said, but it was showing a circuitry problem since that little bitty bulb was burnt out. The bulb was an odd little thing and it couldn't be bought at a parts house. The next thing you know, the mechanics are going through the junk yard, pulling every little bulb they could find. Once you installed a working bulb, the trouble code would instantly go out on it's own.
Not Explorer related, but wanted to share.