How Smart Keys Work

Modern vehicles are often double protected against theft by the use of a "smart key." The first attempt at this kind of devise was to insert a small resistor into the key. The value of that resistance would be read by the ignition, and if it was not a match then the car could not be started. These keys were susceptible to wear, and when the vehicles aged sudden failure could occur. This seldom happened at a convenient location, making the technology unpopular.

Currently, most vehicle keys, particularly on high end models, have a true "smart key." The head of such a key contains a small transponder. A transponder is a device which can receive a radio communication signal and return a response. Many people are unaware that their auto keys have this computer-like ability. There may be no external buttons, and no battery is even required.

When the key is inserted in the ignition and turned the traditional, mechanical ignition lock is worked, the vehicle's computer is energized, which then sends a signal to the key. The transducer will respond and return the code back to the engine. If the code is correct the engine will be unlocked, the car will start. This takes only milliseconds, and users will not notice that there is any wait required before the engine turns over.

Usually a ring antennae is enclosed in the ignition casing. This antennae receives the signal from the engine computer and it then acts as an induction coil, powering the transducer in the key.

Vehicle computers may use a fixed code or rolling code for key verification. Fixed code means that a particular brand and model will use a standard code in every vehicle of that type. These are slightly less secure than a rolling code where each time the key is turned the computer generates a random number which must be returned for ignition to occur. Because unscrupulous people were able to obtain lists of fixed codes, the signal could be returned to the engine with the proper equipment. Nevertheless, since this type of key was introduced in 1995, Ford alone reports a 70% reduction in vehicle theft on their models.

When a driver removes the key from the car and takes it with him or her, this effectively removes one entire component of the power system, making it extremely difficult for anyone to steal the vehicle. Short of having some very sophisticated equipment and a decent amount of time, the car can not be started. Of course, professional thieves will always find ways to compromise a system, but joyriders or those who have a few minutes to "hot wire" a car will be effectively stopped.

These systems give a double layer of automotive security protection: the mechanical ignition lock, and the electronic engine lock.

This technology is, of course, not cheap. The days when you could go to a hardware store and get an extra key for a couple of dollars are past. These keys require special blanks which include the transducer, and often are made of layers of various metals and magnetic materials. If you lose a key, or simply want an extra spare, plan to spend between $30 and $200. The key must not only be cut, but must be programmed with the specific instructions from the manufacturer. Only dealers and professional locksmiths are supposed to be able to obtain these machines.

So, your new vehicle may be much better protected against theft, but be really careful not to lose those keys, or you will quickly learn just how expensive of a mistake that can be.