94 Pont Grand Prix Stock Security bad

Just today my Pontiac Grand Prix stock security system went out (chip in key type). I know this because on the way to work this morning my security light on the dash was on. It also came on this afternoon. In addition, all day it has hesitated to engage starter by about 1 second after turning to start. Then when I finally got home today it is will not start at all, although all systems come on. I tried my spare key to no avail. I am 99 percent sure it is the security system disabling the starter. Now... my Hanes electrical diagram shows a theft deterrent module and relay. I cleaned all the fuses to the circuit. My question is... what is the component most likely to cause this: ignition switch, module, or relay? What am I looking at for cost? Where is the relay or module located on the vehicle (Hanes fails to illustrate this)? Thanks for any information regarding this issue...

Your key has a resistor in it. Use a meter and measure form one side of the key to the other to get the resistance. Next, measure your other key's resistance in the same manner. Both values should match within 10 ohms or so. If they don't then one of the keys is defective and is causing the theft system to activate. I would suspect your every day key to be the culprit if the values are different. If the values are the same then you may have a problem with the ignition cylinder that reads the key when it's in the ignition cylinder. There will be two very small white wires sheathed inside either a black or orange insulation in your ignition harness. Trace these wires to the plug at the base of your steering column. Put a key in the ignition cylinder and use your meter t measure the key's resistance again but place your meter leads one on each white wire termination pin in the plug. The reading should be the same as that recorded when measuring just the key. Turn the ignition switch to the "ON" positon and retest. If the value is different at any time you will need a new ignition switch. The resistance value is stored by the car's ECM and it compares the know acceptable value to what the key in the ignition is showing. If the two match the ECM will allow the starter and fuel pump to work. If not it prevents the car from starting. If you have access to a scan tool, this may help in identifing the problem. If the light came on while driving, I might suspect an electronic component failed. The VATS system only really comes into play during the crank cycle of the ignition switch. If the resistance changes while driving the car won't care until you try to restart it. Check these items and hope for the best. Also check for blown fuses in the fuse box, underhood fuse panel and possibly inside the lower passenger's side dash for a hidden fuse box if it has one.sparky