Air Bag Light Flashing

I just bought a used 97 Tahoe. Had it for a week and now sometimes after the truck has been running for a while, the air bag light flashes. When it is on, I have no throttle control. It flashes in .5 sec intervals. This last for about 10 seconds. After it is done, the transmission shifts extremely hard. It only does this after the air bag light gets done flashing and the hard shifting lasts until I shut off the vehicle. Any ideas? It is 4wd 5.7L

Ok, I cleaned off the grounds and found some corrosion on the battery terminal. Drove the truck all day. Worked great until just now. The heater fan stopped working. I played with the switch but could get nothing. About 20 minutes later, the airbag light came on and flashed again. I payed close attention this time. The lights dimmed down and the engine surged as it flashed. It flashed for 20 seconds then stopped. The truck imediately started shifting hard. I pulled over and turned it off and back on again. The fan now worked and the truck shifted fine. Is there a computer in there somewhere that is shorting out or something? Please help, I will take any suggestion. I just don't want to go to the dealer blind and have them charge me thousands of dollars if it is not needed or it is something I can fix myself.

These can be typical symptoms of the ign switch failing which was problematic in 97's in particular.

This is going to sound real dumb but by IGN, I assume you mean ignition right? Is this something I can do on my own?

Ignition switch, not key cylinder, can't advice you about dyer job, don't know what your experience is. Try autozone.com/repairinfo, may have info there, then you can determine if you can do the job. Remember this should be diagnosed more definitively first.

I wen to Autozone and ordered an IGN switch and also bought a book on how to install it. Looks like the only tricky part is to shut the airbag system off first. After I posted yesterday, I went to Autozone and the heater fan would not work at all. This morning I drove into work to fix my wipers and the fan worked fine. Definately seems to be related to the vehicle heating up. I had the transmission and radiator flushed when I bought the vehicle and all the temps seem to be in spec. Let me know if there is anything else I should pick up along with the IGN switch. Thanks again guys for all the help.