Airbag Impact Sensor?

I am working on a 95 Blazer. The airbag light is on constantly. I found what I think may be an impact sensor hanging loose by the wires underneath. Looks like it was attached to the transmission crossmember by a bracket that has rusted off. It's a 2 inch cube and has a 3 or 4 wire connector going into it. Could someone verify that that's what I'm dealing with. Information on the airbag system seems to be hard to find. I laid this sensor on top of the crossmember and the light went out.

Unless you are trained in Airbags it is best to leave the repair to some one that is.
Sir bags are just like a loaded shotgun.
First.
Codes should be pulled when the light is on.
And go with the repair flow chart for code.

If moving the sensor turned light out .
Could be a bad sensor or wiring.
A short on it can blow air bag.

But be careful out there air bags can save your life or take it in a split second.

Don't know if you're still interested/concerned, but I just went though a whole issue with a 96 SIR problem, same system as your 95. That is the arming sensor for the system you were seeing. There are two impact sensors in the front under the radiator bracket, same size cubes on the right and left. Without it being grounded, i.e. firmly attached, it probably wasn't registering the whole system. Sounds like you figured it out, as the light went out when you laid it on another bracket. As it isn't one of the impact sensors, placement isn't as critical, just needs to be firmly grounded/attached. I'd be really concerned about the rusted through frame cross-member bracket that you mentioned and hopefully replaced...