Security light flashing and car won't start now

Carry it to the GM dealer! By the time you get through throwing parts at it you will have burnt up the difference in letting them fix it versus DIY.

If the security light is on, then you have a failed antitheft system. This light is only for this. If you bypass the system, your car will work perfectly again.
http://vatspasslockpasskeysecurityhelp.yolasite.com/

If your security light is flashing the alarm is active you need to deactivate it

GoodLuck

Your car has a pass lock sensor made on to the ign. lock cylinder. It reads it from the cuts in the key. You may try another key that is not so worn or you may have to get another lock cylinder. Anti-theft computer requires reprogramming procedure with installation.

put key in ignition and turn all the way like your'e going to start it but don't start it. the security light is going to be flashing. leave it for ten minutes like that until the security light turns solid(not blinking). Turn the key to off and then start it. The tumblers in the ignition lock cylinder are no good any more and the ignition switch needs to be replaced and reprogrammed.

If the security light is on, then it can only be one thing. The security system is failing and immobilizing your car. Go to this link and read up on the problem. The security light is a dead give away that the security is messed up. If you have no little black chip in the shaft of your key, then this means you must have a passlock that runs on the transponder. You need the PERMANENT fix from this site. http://vatspasslockpasskeysecurityhelp.yolasite.com/

I had a problem with a 97 Achieva recently.Someone else replaced the PCM/ignition switch and passlock sensor.I replaced the ICP.Engine would turn over but wouldn't start and the security lamp was dim and flashing and then it would go solid.I tried the wait 10 minutes thing but,the light would never go off! I put the original passlock sensor back onto the lock cylinder. But this is what fixed the problem.I cleaned the contacts on the black wires and green on the ignition switch with tv tuner cleaner! After I cleaned those contacts the security light was flashing brightly.So I turned the key to run and left it there.After a few minutes it stayed on solid.I waited about 10 minutes but the light never went out.So I turned off the switch and then tried starting.It started right up and the security lamp flashed and then went off.Has started every time since.Note:I also scraped the pins that I cleaned with the cleaner with a knife.

might be in theft mode.. is security light flashing on instrument cluster....alot of time the chip on the key gets worn down....setting theft mode to invalid

Here is what you do, but only when the SECURITY light flashes - if it is always ON or OFF it's no use.
Turn the key in the ignition to ON.
Wait for exactly 10 minutes ( SECURITY light will flash for 10 minutes and then stay on SOLID)
Turn the key to OFF
Wait 5 seconds.
Turn the key in the ignition to ON.
Wait for exactly 10 minutes.
Turn the key to OFF
Wait 5 seconds.
Turn the key in the ignition to ON.
Wait for exactly 10 minutes.
Turn the ignition OFF.

Start the car normally.
It has relearnt the keycode and you're good to go.
NOTICE - it takes 30 minutes to relearn, that's THREE cycles of ON - 10 minutes - OFF.

Good luck.

Several GM products, including the Chevrolet Impala and Malibu, the Oldsmobile Alero, the Pontiac Grand Prix, and Saturn Ion, have issues with the Security light coming on. This is many times an indication of a failing Body Control Module (BCM). Initially, the Security light will come on then go off, progressing to a constant on light, before the car will refuse to start. Other symptoms may include erratic action of electronics, a clicking sound coming from the glove box, and the air conditioning failing to blow cold air. I recommend a shop that specializes in the electronic systems of vehicles to diagnosis and make the necessary repairs. They should keep the car until they replicate the symptoms described. A new BCM from GM should cost about $230; plan on another $200 for them to diagnose the problem, replace the unit, and program the new unit. The dealers quote between $700 and $1,100 for the same repair. My experience and the experiences I have read on the internet, indicate the new BCM should last only about a year.