I have a 1999 cutlass with radio theft system. I purchase the car with a different radio. This theft system is use if the radio is stolen. The problem is that ever so often the car will not start. The theft system light on the dash board will flash for 10 minutes before I am able to start the car. This can be a real pain in the butt at times. I need to know how to de-activate this device with out the stock radio. Any help would be greatly appreciated.

 

This sounds a lot like a Passlock problem, not a radio theft system. When the radio system thinks it has been stolen, the radio doesn't work. It has nothing to do with preventing the car from starting.
Here is a link to a fix for your problem: https://oldsmobileforum.com/forum/alero-21/fix-passlock-problems-1194/

 

Your right, it is the passlock system. I came across this after I posted my problem. Thanks.