how do i reset the dash Security light on my 1999 Pontiac firebird

You have GMs VATS security system, which I am very familiar with thanks to my 94 Fleetwood! The number one problem with this system is the ignition lock cylinder! There's two tiny wires inside the lock cylinder that contact the chip on the ignition key when you put the key in the lock. Over time these wires break and the contact with the key is lost so the computer thinks you're trying to start the engine without a key! With the key in the ignition you need to unplug the two wires coming from the lock cylinder from under the dash near the base of the steering column. Measure the resistance value between the two wires. If you can't get a reading, the lock cylinder is bad. The new lock will come with a template for cutting new VATS keys BUT you MUST get the correct key, there were 15 possibilities, in order for the engine to start and run. To determine which key you have measure the resistance value of the chip on the ignition key and compare the reading to the chart below. This will tell you which key the computer will recognize. If you do get a resistance value when you check the wires coming from the ignition lock cylinder move the lock through all the positions to be sure you don't have an erratic reading. If that checks out you'll need to pull the trouble codes from the BCM (Body Control Module) to find out what's going on. If the lock cylinder checks out and you have no codes from the BCM, replace the BCM. Hope that helps! Jim