My wife's 2003 Trailblazer just had a similar thing happen with the airbags. Light would come on but no DTC sent. The dealer actually had to get a special scanner specifically for the SDM. They were then able to diagnose the issue as a bad coil ( part of the deployment system ). Luckily, we were still under warranty. I did see the actual repair bill and it was nearly $1600 bucks.
I do think her dealer is being rather vague, tho. Push harder, if they are gonna charge you for work they MUST provide a detailed listing of what and why. This is especially true in CA, land of the class action lawsuit ( the lawyers get paid better this way ).
Good luck, let us know how things come out.

 

thanks you guys, she is bringing the burban to phx for thanksgiving and will be here this sat. i will get the codes and check the wires to the sdm then. keep posting any ideas you all might have of things i can check out. i'll post back when i get my hands on it. thanks again

 

Man,the prices are unreal...what is it about a fuel pump that makes it cost 650.00?

The air bag stuff doesn't even have to work unless there's a impact sufficient to blow the bags,right? How can the components wear out? Sounds like a defective part(s) or maybe a bad connection like chevymec said. I can see why a woman would want it to work,especially if she had kids. I'd let it go rather than pay that or get the stuff from a junk yard, which would still be pretty high.