Light flashes security , wont start wait exactly 10 minutes starts right up happen maybe twice a week 1 time out of 20. Whats up?

OK. you had the battery disconnected. Here is what you do. Turn on the key. The security light will begin to flash. Wait (about 10 minutes) with the key in the ON position. The security light will stop flashing. TURN OFF the key. Then, turn on the key and start the car. Security system is supposed to prevent theft for a 10 minute delay. This usually discourages any thief. This will work, You just need to be patient with the 10 minutes. It seems like an hour when you wait ten minutes for that security light to stop flashing.

Instructions

1. • 1 Attempt to start the car. If it does not start, or dies very quickly after it started, then leave the key in the ignition in the "ON" position and wait 10 minutes. Make sure the security light is flashing. After 10 minutes the security light will stop flashing and either turn off or stay on steadily. When it does, then turn the ignition off, wait 20 seconds and attempt to restart the car.
     
   • 2 Repeat this procedure three times in quick succession without removing the key from the ignition.
     
   • 3 Start the car following the third 10-minute waiting period. The car should start and stay on. If it stays running, then the codes have been relearned and the problem is solved. If the car still does not start then you may need to have all or part of the passlock system replaced
     

I OWN a 2001 Olds Alero and the same thing happens to mine.. It's an easy fix..
1. Turn the Key to ACC (keep it in this mode for the entire 10 minutes).
2. The security light on the Dashboard will flash for exactly 10 minutes..
3. Once the 10 mins are over, the security light will stay solid..
Wait for the red light to disappear off the dashboard...
YOU ARE NOW READY TO TURN YOUR CAR OFF AND RESTART YOU CAR....

SIMPLE FIX..
I DO THIS ALL THE TIME TO MINE..

GM's are known for possessing faulty antitheft systems. When these systems being to fail, the antitheft misinterprets the failure as an attempt to steal the vehicle. The system then shuts off the injectors. The system resets after 10 minutes exactly. As the fault gets worse, this will happen more often. Next time this happens, note any lights that illuminate on the dash area. If you see one that says SECURITY or ANTITHEFT, this is most likely the problem. This link will help you.
http://vatspasslockpasskeysecurityhelp.yolasite.com/

It's could be your PassLock security system that is failing. It started happening earlier this year on my 2002 Impala. If you wait about 20 minutes, it's starts right up after it resets. It started to happen every couple weeks and then every couple days, after a few months. I ended up bypassing the security by soldering in some resistors.

See the pictures at:
http://s2.photobucket.com/albums/y48/ZeeVert/2002%20Impala/PassLock%20Bypass%202011/
It took me about two hours to take apart the dash and carefuly double check everything I did, and take pictures. If I did it again... maybe 45-60 minutes (plus getting resistors).
I was lucky to have some resistors close to what I needed, so it cost me nothing but some time.

My ignition resistance checked at 1250 ohms. I used three resistors totaling about 1400 ohms. (At least according to my $10 meter).
Seems to work, even after I disconnected & reconnected the battery.

turn the key on and wait till the security light stops flashing ( this could take as long as 30 minuets ) then turn the key off then back on but do not try to start the engine and wait till the security light stops flashing ( again this could take as long as 30 minuets ) then turn key off then turn key on and start engine.

Gm downfall, It needs repair to the passive theft system

im just gonna take a stab in the dark here i understand that your security light is on try unlocking your door with your key sometimes you just need to reset the security. otherwise ive seen a security module go bad that may be preventing you from starting it.

You could try resetting the computer. The car maybe in lockout mode. Try turning your car over….leave the ignition on. Wait exactly 10 min. Then try turning over again….again leave the key on. Wait exactly 10 min and do it a third time….this time the car should start…maybe run a lil rough while it relearns the processes of your vehicle again. It is important to wait the exact 10 min each time. You will probably need a battery charger or a set of jumper cables because if your car goes low during this process it will not work. Good luck and I hope this works.

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.