2006 GMC Sierra

2006 GMC Sierra V8 Four Wheel Drive Automatic

I have a 2006 GMC Sierra Z71, the air bag light is on, and service air bag message is lit, we took it to gm and they told us the air bag coil is gone, and would cost 800.00 to fix, just wondering what the actual name of the item is so that I can look for the part cheaper, and if you thinks this is actually the problem?