I have a 2002 chevrolet impala and it does not want to start.the security light is on. is there something i can do to make it work again

SOURCE: why did the security light come on in my 2003

That indicates there is a pass-code error. There are a few reasons why. Easiest way to explain it, is that your key has a "chip" in it, with a resistance or "password" that your cars computer is looking for. It means that your cars computer did not see the right password. It will probably reset itself once it sees the correct password a few times. If not, you want to get it checked, because if it happens too often, the vehicle will not start.

The causes for this problem on these vehicles are generally the ignition switch or passlock sensor. There is also sometimes a water leak that occurs at the right front cowl, check the inside passenger side floor area, if it is wet. It could then be a BCM problem. Goodluck

Joe Taylor

• 2229 Answers
• Posted on May 01, 2014

SOURCE: 2005 chevrolet impala won't start, security light flashes

The security icon is a visual indication that something in the car's antitheft system is failing. In most GM cars and trucks there is a hidden system that most people are unaware even exists. From the moment you put your key in the ignition, there begins a constant line of communication between your key's security chip or transponder, to the ignition's lock cylinder, and then to the car's TDM (Theft Deterrent Module). These 3 parts are in CONSTANT communication. If the key is in the ignition, then these parts are sending signals to each other. The security light illuminates when that signal gets broken, even just for a second. When the signal breaks, the car misinterprets this as an attempt at theft and goes into antitheft mode. The car thinks its being stolen or hotwired because it is not getting that signal from YOUR specific key. This is why the security light turns on and shuts down your vehicle. This link explains it pretty well.
http://vatspasslockpasskeysecurityhelp.yolasite.com/