Theft system light comes on - 1998 Cadillac DeVille

When the anti-theft system in your car is activated, it is designed to prevent unauthorized access to the vehicle and protect it from theft. The specific features and functions affected by the activation of the anti-theft system can vary depending on the make and model of your car. However, here are some common ways in which the anti-theft system can impact your vehicle:

1. Ignition Interlock: In many vehicles, the anti-theft system can prevent the engine from starting or cut off power to the ignition system. This is often the primary function of the anti-theft system to deter thieves from driving the vehicle.
2. Key Removal: Some anti-theft systems can also lock the key in the ignition switch, making it difficult or impossible to remove the key when the system is activated.
3. Door Locks: The anti-theft system may lock or unlock the doors automatically when it is activated. This can be intended to prevent unauthorized entry.
4. Windows and Sunroof: In some cases, the anti-theft system can disable the power windows and sunroof to prevent someone from gaining access to the interior through these openings.
5. Alarm Activation: If your vehicle is equipped with a security alarm system as part of the anti-theft system, it may activate the alarm if unauthorized entry is detected or if someone tries to tamper with the vehicle.
6. Vehicle Immobilization: Some advanced anti-theft systems can immobilize the vehicle by cutting off fuel or electrical power to the engine.

If you're experiencing issues with your key not coming out, windows not rolling down, and the sunroof not opening, it's possible that these problems are related to the activation or malfunction of the anti-theft system. However, it's essential to consult your vehicle's owner's manual or contact the manufacturer or a qualified automotive technician for specific information about how your vehicle's anti-theft system operates and to diagnose and resolve the issues you're facing.

In many cases, anti-theft system problems may require specialized equipment and knowledge to diagnose and repair, so seeking professional assistance is often the best course of action.

Do you have a second key to the car if so try it, could be the key is the problem. Has the battery died or been disconnected may need to a relearn, some suggestions and thoughts in links below.
I have a 1999 oldsmobile cutlass, the "theft system" light is coming on. as you well know you cant start the car for 10 (justanswer.com)

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Your vehicle has two theft systems - content theft , if the door is opened without the key or keyless entry key fob the horn honks lights flash . PATS - passive anti-theft system ,this keeps the vehicle from starting if the computers don't see the right code from the transponder pellet in the head of the key .
You can turn off the content theft but not the PATS , when trying to start the vehicle does the theft light flash fast ? Red light on top of the dash .

The theft light 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 misinterperates this as an attempt at theft and goes into antitheft mode. The car thinks its being stolen or hot wired 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/

I have had the same problem. This has happened to me three times in the past nine months or so. Per the owner's manual, you turn the key to the on position and wait about ten minutes. This resets the system and when the "Theft System" light goes out, it starts right up. I did this each time and it started right up.

Turn the key forward 2 clicks, but don't start it. leave like this for ten minutes, no less. Turn key back, then forward to start the car.

the instrument cluster is probly failin-can happen with age or if u spiked it by puttin a new battery in car-these things are really sensitive to voltage swings--may also be a wiring issue too--get car scanned at a discount place and buy a haynes manual

all you need to do when the theft system comes on is turn the key to the on position do not start and let is sit till the theft system light is off. you will kinda bypass the theft system it is not a permanent fix but it will work. you can take the vehicle in and get the theft system taken out or replaced

its a theft system that comes standard just turn the key to the on position do not start. leave it like that till the theft system is off.

No, I think he has the same problem I do. I have a stock 99 malibu...no real theft system. Usually after it rains or gets cold, a "theft system" light comes on in my dash. I can be driving, and the light will come on. If I turn the car off, I cannot restart the vehicle till about 20 minutes have passed and the light finally goes off. Sometimes this light comes on when I try to start the car in the morning. I put the key in the ignition, and the car will not start for 20 minutes till the darn theft system light goes off. From what I gathered, the theft system issue has something to do with a "passlock II" defect. I have no idea what this is, all I know is that I can't get a mechanic to listen to me, because the issue never repeats itself when I go to a garage. It gets a little annoying, but I've learned to deal with it.