Does the airbag system rely on the Powertrain Control Module for any reason (Speed, ABS application, or anything?

If one were to strip out an Excursion of everything except the airbag electronics and roll it down a hill into a brick wall, would the airbags still function?

 

Yes to the first sentence! If things haven't changed since my ASE cert days....there is a module that reads speed and deceleration in the Air bag system. There should be 4 sensors on the vehicle. Like I said 18 years ago that was how it worked.

Not sure to the second. I would think if you totally gutted all the electronics there would be nothing to send a signal to the firing mechanism in the Air Bags. Plus if you took out the Batteries there would be no power.

Finally WTH would you want to do this?

 

Diesel conversion. Cummins to be exact.

Can't make a Dodge/Cummins PCM talk to the airbag control module.
Hell, a 12 valve doesn't even have a PCM if I go the full mechanical route. The engine just needs a single 12 volt wire to activate the fuel cutoff solenoid... And even that can be replaced by a simple pull cable

 

I know that some airbag modules contain a capacitor that stores enough energy to trigger the airbag in the event that a battery cable was severed etc. Not sure which vehicles have this feature though.

 

Well there is a company that does those swaps ad then sells the Ex's. I can not find the link to the website. Might want to ask someone that does the swaps on a regular basis.