The car want start i think its the key because someone tried to steal the car before

It's the "someone is trying to steal me" sensor that plagues us all with GM cars during that time frame. They can program the computer to ignore it, but they charge about $200 for it. It actually occurs as the ignition gets worn, and starts to feel the key a little less, and thinks that someone it trying to pick it.

Just a shot in the dark. If your key has the magnetic chip in it, the chip may be week. Try another key if you have one.
We have a key without a chip in it we hide under the car. It will turn the ignition but will not crank(dealer told us that). One more thing the dealer who made the key told us not to try cranking the car with it because the car could think someone is stealing it and shut down till a dealer input codes to allow the car to run again.

i had tjis problem it is a security tking the car simply does not recognize your key thinks someone trying to steal solution turn key all the way to on as if starting let go wait 10 min when security light stops flashing and is steady turn key to off then restart note you have to wait the full 10 min if you dont car will not reset security and you will have to start over

you are not turning it back far enough you just think you are replacement switchs need to be turn back way back then remove key

what makes you think someone tried to steal it? the security light issue is a very common problem with GM cars equipped with the Passlock II anti-theft system. just a few days ago my 2003 impala did the same thing in front of a 7-11. took me about 10-15 minuts to get it started. i just kept turning the key on, tried to crank it, and turned the key off numerous times. i had a 1999 malibu that did the same thing and i replaced the ignition cylinder and keys. that cost me about $160 but it solved the problem. changing it out is fairly simple. if thats the route you have to/ need to go i can walk you through it. unfortunately however, GM, although this is a very common occurance, will not issue a recall to fix the problem.

the clue is the fast blinking theft light,you may need to recode your keys to the car.as the car thinks someone is trying to steal it.....

your car was build with an anti-theft devise from GM, inside the ignition key is a micro-chip, when you insert the key in the ignition cylinder, the sensor inside the cylinder will measure the resistance of that micro-chip inside the key, if there is a match the engine will start, if no match the computer will think someone is trying to steal your car & shut it off.
try using another ignition key (spare key) if this doesn't work most likely the tiny wire inside the ignition cylinder is broken therefore the ignition cylinder will need to be replaced.

The car is not reading the key and thinks someone is trying to steal it. Try another key or see a dealer.

The alarm system 'thinks' someone was trying to steal the car. You will have to reset it.
Try this;
remove key from ignition.
lock and open the car door with the key as normal.
or disconnect/wait a while/reconnect the battery
or you may have to contact the alarm manufacturer.