Wont turn over antitheft device preventing car from starting only have 1 key and it is the orriginal what do i do

it appears you may have tried using the wrong key to start the car and the antitheft system engaged to protect the car from being stolen or driven insert the correct key and the antitheft system will turn off and allow you to start your car

acquire? (you have one now, my guess you mean buy spare?)
id bet $5 is not bad, just the key ,is, so many people drive with only 1 key, and this always happens....
this part is the immoblizer part... (no alarm part)
the key is bad, lost the spare? this be first step.,...
it has to like your key, that is its #1 purpose,
first is to check all fuses. there are many fuses related to
the antitheft option.
Fuses:
clock dome fuse? and C13 fuse (antitheft)
this module kills the starter relay dead. (can be bypasses ask)
finding a 2nd key or fixing antitheft on any Isuzu (they bugged out in usa, )
can be hard finding support for isuzu, in usa, (like Yugo,Daewoo,and suzuki.)


try my hack.
this blu wire if grounded, enables the starter relay.
give it a try.
theory, when the Anti box likes your key.
it grounds pin28 and the starter relay wakes up.
the key start wire powers the starter relay on its other coil pin.

The antitheft picture/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/

Place the key in the ignition, and turn it slightly to the right. Don't try to start it. When you turn the key the dash lights should have lit up. Keep the key that way for ten minutes, maybe a little more. The theft system light should turn off, and the car can be started.

Antitheft or Security system failure is a common problem on GM vehicles. Every time you put your key in the ignition, the vehicle's security system reads the signal from your key to make sure it is OK to run. When it recieves the "correct key" signal, the security system allows the starter to turn over, and/or the fuel injectors to function and your car works like it normally does every day. If you were to use a different key, or try to hotwire it, the system would shut down these parts of your car, thus making the vehicle completely immobile. This is GM's way of preventing vehicle theft. The problem is that the system is known to fail quite commonly. It has been failing consistantly for around 30 years. When it fails, two things can happen. First, you turn the key and nothing happens at all. Lights work, radio works, windows work... just not the starter that you need to start the vehicle. This is a "starter immobilizor". Second, you turn the key and the vehicles starts just fine, but then stalls in 2-5 seconds. This is a "fuel immobilizor". It literally cuts off the fuel injectors and stalls the vehicle to immobilize it. These are normally followed by a light on the dash that says SECURITY or ANTITHEFT. These lights are to inform you of the system's failure to collect the information it needs from your key to the computer. If your security/antitheft light is on, odds are you will be stranded soon, if not already. There is a lot of info on this site that you can read up on. http://vatspasslockpasskeysecurityhelp.yolasite.com/

try a new battery in the car if old one is low on power the antitheft device kicks in as thinks its being stolen ,after installing new battery lock an unlock vehicle with the remote and then start as normal

Yes, if you did not have a key made to fit the new lock that matches the old chip.

Depending on the year of your pontiac, the antitheft system may be preventing you from starting. Go to this link.

http://vatspasslockpasskeysecurityhelp.yolasite.com/

Alot of the time, "no start" situations can be traced back to the antitheft system. Especially in GM vehicles like your Cadillac. When this system fails, the antitheft system doesn't get the proper signal from your key. This puts they car into antitheft mode and turns off the starter to prevent theft. This may be your problem and worth looking into. Here iss a link that explains all about it.

http://vatspasslockpasskeysecurityhelp.yolasite.com/

Unlock the drivers door with the key