Monte Carlo Will Not Start. Security Light Blinking. Put A New Starter On And Still Will Not Start.What's The Matter?

The neutral safety switch is located on your transmission where the shifter linkage connects.
I think by 2001, it is now referred to as a, manual lever position sensor.
If it is bad, your car would not crank.
It is not that difficult of a repair, if you are mechanically inclined.
If that is the problem, the best I can remember, is that there are three torques head bolts and an electrical harness connector, that you push on the tab and pull to unplug. Of course you have to separate the linkage from the switch first.

The problem is in the chip that is in your key, the computer can't see that ypu put in the key. this can be a very expensive repair.

You'd need to either (A) Come from the top by removing the selector face plate (the thing with P-R-N-D-3-2-1) and work down to it from there, or (B) work UP to it from under the car. I'm not sure on it's location with your car with mine you have to get to it from underneath and it's a right pain in the ass.

Where is this linkage located and how do I get to is. We took out the air box and seen the switch. Thanks for the help

If there is no effect on your cars performance it is probably a glitch in your computer you can have reset at dealership usually at little expense

Turn key on and lit it sit for a least 10 min then try to start see your book for security system reset