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Understanding Your Vehicle's Smart Key

Joan Young By Joan Young on
Badge: Editor | Level: 34 | Cars & Motorcycles Expertise:

A smart key is one which contains a small electronic component called a transducer. This provides an extra level of security against theft for your vehicle, beyond the mechanical ignition lock. Beginning in 1995 some high end vehicles were supplied with smart keys. Now, many vehicles include this feature, and owners may not even realize it.

A transducer is simply a small device that can receive a signal from an external source, and return it. This is found in the head of many car keys. It is designed to “speak” to the computer in your car’s engine. When you put the key in the ignition and turn it, this activates the car’s computer. The car then sends a signal to the key.

“But wait! How is the key powered?” you ask. If the key doesn’t remotely operate locks or the starter then you don’t have to change any battery in the key. How can it have a mini-computer? Very ingeniously, the casing around the ignition contains an induction coil, called a ring antennae. This creates an electric current that powers the key.

The computer sends a signal to the key which must be returned correctly. If it is not correct the computer will not allow the engine to start.

When you leave your vehicle and take the key with you, you are physically removing one required element from the ignition process that is not easily overcome by thieves. Since the introduction of smart keys, auto theft has dropped significantly. Hot wiring a vehicle so equipped is not possible. It takes a very sophisticated thief, with expensive equipment to overcome this electronic lock. This effectively ends the work of joyriders and unprepared criminals.

There are two kinds of signals used. Some vehicles use a fixed signal, which means that for a certain car make and model the signal sent to the key is always the same. This is easier for professional thieves to defeat because lists of those codes can be obtained illegally. They still need the equipment to mimic the electronics in the smart key, and also overcome the mechanical lock.

The other type of signal is a rolling signal. This means that every time the engine sends a signal to the key the number is randomly generated. These are much more secure, even from professionals, because at this level they must bring equipment that can exactly duplicate the key– both reading the signal and returning it. Again, the mechanical ignition lock also has to be bypassed.

All of this complexity is what makes newer car keys cost a small fortune. If you lose a car key, you can expect to pay from $30 to $200 to have it replaced at a dealership or an approved locksmith shop. The cost will be the same even for a duplicate. The days of going to the hardware store and getting a spare car key are over. In exchange, the level of protection is increased significantly.