The way I am understanding what you are saying- the 10 minute procedure quit working and you bought a new cylinder pass lock sensor. Here is what you may have to do. If this doesn't work then you will have to have a dealer cut you a brand new key. Did you get a new key with the cylinder? I am assuming that you did. Try this. It worked great on mine.: 1. turn the key as if you are starting it, then let off pressure and let the key go to the "run" position. Now watch the security light for 10 minutes(if it is working, you will see the security light blink and your battery light will blink) 2. After 10 minutes has passed, turn the key to the off position and wait for 5 seconds. Then Turn the key to the start position again and let the key go back to the "run" position. Now watch the security light again to see how many times it is blinking. Complete the sequence and do it one more time if you have to. Note: What you are doing is reprogramming the body computer with the key switch. If this procedure worked before the third time that you used this 10 minute procedure, then you have solved the problem. One important thing to remember is don't put a lot of heavy objects on your key chain. Too much weight on the key will mess it up again.
This is a VERY well-known problem & was even a recall on some GM's ...spray a squirt of WD-40 or tv tuner spray into the ignition switches' keyhole, ram the key in & out, wiggling it around when it's in, and that should "feed it an aspirin" till you have the ignition switch replaced @ a dealer. Also, Mine needed the main computer ("body control module") replaced as, not only did it do the weird "security thing", but my headlights would intermittently flash on & off, dome light came on whenever it wanted (ran battery dead a few times) & some other weird things. Costed $1800 dollars to have BOTH done ...thank GOD I bought a warranty when I bought it at a used car lot!!!
