99 key question
 

Ok I got 99 rodo my girl got a grand prix
Ok now I tryed a copyed key in her car and would not start like it should so why in my copyed key working in my truck and running ??? Now the I had problems with truck not starting cuz of security system thinking I am stealing it so why if I use wrong key it works ??

Long story short 99 Silverado 1500 v8 have a security key or what need to fix security system locking me out now and then did relearning crap didn't work was thinking about key cylinder replacement

I have a 99 and copied keys work in it. There is no chip in my keys. The Grand Prix might have a security chip in the key.

So then were is security start then if not in the key I know security if messed up do I start with key cylinder

If the key turns and the engine cranks but does not start then the cylinder is good. Do they start with the original key? Only a few key shops make the security key. Any GM dealer should have them, but they are expensive.

No here is problem and from what I seen its a tm thing
Ok so now and then truck won't start security light will flash truck thinks I am stealing it if I wait it will after 10 min then its fine so I tried to relearn key but if it don't have a chip no need
So I need to know were security starts if not the key how does truck know its getting stolen

Oldchevy were does security system start if no chip in key

As far as I know there is no factory security for my 99 Silverado. A copied key starts my truck. I think you get the security with aftermarket alarms if you want to pay for them.

Most 99 anything have the Passlock vehicle theft deterrent system. The Passlock sensor built into the lock cylinder is designed to detect a tamper (forced turning or something hammered in, etc.) and thus a copied key will work fine as long as it can smoothly turn the lock cylinder. A flashing SECURITY light means either a damaged Passlock sensor or worn ignition switch that causes voltage fluctuations downstream. My standard recommendation is to replace both the lock cylinder (rekeyed to the original key) and ignition switch.

So its like a mercury thing on bomb lol only thing I know that works like that
If I hit or bump start it it will not work ??? That's not really security but it sure stops me from driving for 10 min lol

No, it won't work and it's not going to get better. It's 10 minutes now but eventually no-start ever. It's best to take care of it before needing towing and possibly missing work.