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There are a couple ways you can disarm it. The easiest way is the key fob. Pressing the unlock button on the fob disarms it. If your fob doesn't work or you don't have one for some reason, you can disarm it by unlocking any of the doors with the key. Unlocking the driver's or passenger door with the key, or unlocking the trunk with the key will do it. Often the disarm switch in the driver's door can stop working because it's the one most used, so tryhing the passenger door or trunk may do the trick for you.
Are you saying that the engine doesn't crank? The starter does not engage and turn the engine over at all? No noise from the engine compartment? If it were the factory security giving the problem it would start and run for two seconds and die every time. Is this what is happening?
Have you checked the battery voltage with a voltmeter? We'll need to start with that. You are looking for about 12.6v at the jump start posts.
How did this problem start? Had you done any repairs? Was it running fine and then you tried to start it and found this?
Have you checked all fuses in the box under the hood and in the dash?
Where exactly were the wires that were cut under the hood? Were each of them soldered back together and isolated from each other?
Have you checked every fuse?