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Immobilizers have been around for years and are available in a few different designs but they all have one job; to stop people from borrowing your car without your permission. These electronic devices automatically shut down essential systems in your car to prevent the engine from starting. This includes shutting down devices such as the fuel pump, starter motor or fuel injectors. Should a thief try to steal your car, he won’t get far once these essential systems shut down. For those do-it-yourself mechanics that are used to carburetors, this is usually a nightmare of a system to work with, but it does its job. Intrigued? Here is a bit of knowledge on different immobilizers and theft deterrent technology.
Types of Immobilizers
1. General Motors (GM) PASS-Key I/II and VATS: The term Passkey and VATS are interchangeable terms in this article. The Passkey I was the first passive immobilizer. It was introduced back in 1986 on a corvette. Passkey I systems have a visible resistor “pellet” that is easily recognizable in comparison to other keys. Many people call the pellet a “chip” thinking that it’s some sophisticated theft system using advanced computer technology. However, this is not the case; it’s actually a very simple system. That visible resistor is not a computer chip; it is a little block of carbon sized to have a special resistance value. The decoder built into the car recognizes this resistance value and enables the fuel systems and engine cranking. Passkey II systems are relatively the same, the only difference is in regards to some of the hardware built into the car. The whole system is controlled by a black box called the TDM (Theft Deterrent Module). This list shows the resistance values of the different key blanks:
|Key Blank Number||Design Resistance||Minimum Resistance||Maximum Resistance|
Types of Immobilizer Bypasses
Bypassing GM Passkey I/II and Passlock I/II: Most of these systems can be bypassed using resistors and relays, but occasionally manufactures have bypasses available to simplify the process. Usually these manufacturer created bypasses are connected close to the remote start connections. Some vehicles have bypasses designed for them that will not work or could be incorrect. Make sure to do your research or give us a call to ensure that you select the right one for your vehicle.
Bypassing Transponder Based Systems: Generally there are three types of bypasses available for transponder based systems. Sometimes not all three versions are available for a specific vehicle. I will provide you with a bit of information about each kind, including the pros and cons.
1. Universal Bypass: These systems bypass the immobilizer during remote start by taking the signal from your key and sending it through a ring around the key cylinder into the factory antenna. The problem with this system is that it requires you to place your key in the box and mount it under the dash, so you effectively lose a key. They tend to be easy to connect, requiring few wire connections, but they can be sensitive to cold temperatures. Because it is universal, it will work with most vehicles so long as you give up a key.
2. Vehicle Specific RF Bypass: The RF bypass works the same as the universal bypass except there is a chip that is programmed to the car. This means you do not have to sacrifice one of your expensive keys. These systems are not available for all vehicles unfortunately and they can be sensitive to colder temperatures. On the plus side they require few wiring connections and do not use an extra key.
3. Vehicle Specific Data Bypass: These data bypass modules have been around for about 6 years now and connect directly to the wires of your vehicle. When you activate remote start, it will send a data signal directly to the car’s computer enabling it to start. This system is reliable in all temperatures and will not use an extra key to function. Unfortunately they can be rare and they are not available for all vehicles. They also require more wire connections to the car.
Written by Kyle Duffy
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