i heard it could be the theft deterant system causing the tahoe to do this i thought it was maybe the idle control valve ,but this morning i went to start it and it did the same thing again,How hard is it to fix this theft system and can i do it or does it need to go to the shop?

your problem most likely is the theft system. If you get in a pinch you can turn the key to accessory and you will have to leave it on until the security light is no longer on. takes about 15 minutes. it will start and should stay running long enough to take it to your shop. you have to replace the ignition cylinder and have the security reset. I have had two done. GM dealer charges approx $170-200 parts & labor. hope that helps

your problem most likely is the theft system. If you get in a pinch you can turn the key to accessory and you will have to leave it on until the security light is no longer on. takes about 15 minutes. it will start and should stay running long enough to take it to your shop. you have to replace the ignition cylinder and have the security reset. I have had two done. GM dealer charges approx $170-200 parts & labor. hope that helps

is there any way to just disconnect the security system and replace it with an after market one?

your problem most likely is the theft system. If you get in a pinch you can turn the key to accessory and you will have to leave it on until the security light is no longer on. takes about 15 minutes. it will start and should stay running long enough to take it to your shop. you have to replace the ignition cylinder and have the security reset. I have had two done. GM dealer charges approx $170-200 parts & labor. hope that helps
is there any way to just disconnect the security system and replace it with an after market one?

is there any way to just disconnect the security system and replace it with an after market one?

No.
After market only adds up to more problems.
Best to get it put on a engine capable scanner and find what part of anti theft is bad.
There should be a code set if it is acting up.
Post back codes.
MT