When Mary Elizabeth Schuppin lost the keys to her new Toyota Avalon, she didn't think much about it. After all, how hard could it be to get her local Toyota dealer to make a new set?

A lot harder than she ever would have believed. Unless she found her keys, the dealer told her, it would cost her $2,400 if she wanted to continue using the sophisticated security system that came with her $30,000 car.

"When they told me that I really started looking for my key," said the retired schoolteacher from Fairfax Station.

The Avalon was equipped with Toyota's computer-operated "engine immobilizer system," designed to keep even the most sophisticated thief from stealing the car because it immobilizes the engine, fuel system and transmission unless a proper key is used. And if you happen to have lost the car's "master key," as Schuppin had, it will keep you out just as easily.

According to Toyota, what happened to Schuppin could happen to anyone. Because she had lost her master key, there was no way the dealer could make a new key that would work with her security system and allow her to start the car. The only way to keep the security system intact, the company said, would be to install a new computer system.

The immobilizer-type security system, the latest high-tech device for thwarting car thieves, is an option on premium Toyotas and almost all of Toyota's Lexus models. In addition, some of the luxury European cars, such as Mercedes-Benz, and General Motors and Ford offer similar systems.

But only Toyota appears to require a whole new computer system when the master key is lost. While Toyota officials say this is rarely a problem, the car's manual is vague on the potential consequences. One section reminds owners to keep the key number, while another notes that both the key number and master key are needed to make a new key.

In the Toyota system, according to company officials, the computer chip in the key is an electronic Rosetta stone that communicates with a computer system connected to the engine, known as the engine control module (ECM). Every time the car is started, the ECM commands the key to roll to a new code in a random sequence. The ECM can track multiple keys to the same car separately.

The ECM can be reprogrammed a limited number of times as long as the owner has a master key. But if the owner loses the master key, as Schuppin did, the ECM cannot be reprogrammed to learn or unlearn any other keys.

"Without the master key, you have to buy a new ECM and master key set," Toyota said yesterday.

Toyota officials said the company had taken notice of the "potential downside" of its new security system but decided against changing it "because to do so would significantly compromise security." Specifically, a company official said, allowing dealers to reprogram the ECM could also allow thieves to somehow get "their hands on the secret software or tool to reprogram the car."

With the surge in sales of luxury cars in recent years there has been a boom in the car-security market. Bill Groat of the Specialty Equipment Market Association pegged the market at $340 million last year and growing. Since 1994, SEMA estimates, the market has increased 111 percent. "I think it's come a long way because the criminals are becoming more sophisticated and seem almost to be a step ahead of the market," he said.

Theft-deterrent systems have come a long way since the introduction of the "Club," the metal steering-wheel handcuffs that sell for less than $50.

Mercedes-Benz, one of the world's premier makers of luxury cars, now routinely installs such systems in its cars, which range in price from $31,000 to more than $138,000. "These cars are designed not to be started in any way but the proper way," said Mark Zetlin, Mercedes-Benz sales manager at American Service Center in Arlington.

Zetlin said each Mercedes-Benz customer is given two "smart keys" equipped with computer chips and one non-electronic spare key.

"It is extremely unlikely that an owner would lose both smart keys," Zetlin said. But should such an unlikely event occur, he said, "they would have to order another key." Unlike Toyota dealers, a Mercedes dealer can reset the codes in the ignition, engine and related drivetrain systems, Zetlin said. The cost per lost key is about $150.

General Motors' PassKey system works pretty much the same way but is somewhat less sophisticated. Customers can order replacement keys and the anti-theft system is reset. GM officials said the cost of replacing lost keys and resetting the computer range from $90 to $150. Ford dealers can also reprogram that carmaker's Securilock system.

And how has Mary Elizabeth Schuppin fared?

"We found the keys," she said yesterday. And for $45 each she had two new master keys made. "I'm putting one in the safe-deposit box," she said.

How Toyota's "engine immobilizer system" works:

Every time the car is started, the security system commands the key to roll to a new code in a random sequence; if the wrong key is used, the car's power train will become disabled.

The system can separately track multiple keys to the same car, so each key is always on a different code.

If keys other than the master are lost, the system can be reprogrammed to ignore a lost key and learn a new key.

If the master key is lost, the system will still recognize the other keys, but it can't be reprogrammed to learn or unlearn any other keys.

To get a new master key, a new security system and master key set must be bought.

SOURCE: Toyota