Locking in to key secrets

The key and its communication with the vehicle carry all sorts of complex codes. Photo / Supplied

The bigger the car market the higher the cost of replacement keys - that seems to be the rule of thumb after a study comparing prices between New Zealand and Australia.

Lose the keys to a BMW or Mercedes-Benz across the ditch and you face a replacement bill of up to A$800, or nearly $1000.

Do the same here and both Germans will charge between $450 and $650, depending on the model. Jaguar in this country will relieve you of between $625 and $800.

Subaru, on the other hand, will ask a modest $25 for the key to an older Legacy or Impreza - or up to $550 for the latest whizzbang device. Subaru Australia wants A$665 ($840) for the latest Legacy, plus the cost of cutting.

"The key for a car in the old days was simply a steel plate cut to shape and replacement was a matter of getting a local locksmith to sort it out," says Subaru New Zealand managing director Wally Dumper.

"But today's keys have transponders with rolling codes and most don't even have a pointy bit you poke into the ignition any more."

Most carmakers in New Zealand will replace modern keys within a working week or so, sometimes sooner. But replacements for top-end European models have been known to take up to six weeks.

Technology is driving up the cost of the humble car key, although most car distributors here try to keep replacement keys for common models at a reasonable price.

There are a number of variables that come into play when replacing keys, including the car's country of origin, the model of the car, the year it was made, whether it is a flip-key or a smart key or a regular three-button fob. Whether your car came with one or two keys from the factory can play a big part too. Almost all car keys on the market now include a remote locking button, so replacement keys not only need to be cut, but also need to be coded to match the vehicle.

In most cases, though, cutting the key and programming the electronics pale in comparison to the actual cost of the replacement remote unit.

Mitsubishi NZ sells around 180 replacement keys a year, all with vehicle immobilisers built in. They are priced between $300 to $500 - before cutting and registration costs.

"Vehicle theft is big business and manufacturers put in place sophisticated strategies to try to foil the most determined car thief," says Mitsubishi's technical services manager Lloyd Robinson.

"The key and its communication with the vehicle need to be very complex, beyond the physical shape of the key profile.

"Rolling codes, signal generators and receptors make up the communication parameters involved in determining that the correct code is being used to start the vehicle."

Nissan keys are priced between $41.47 for the Navara commercial through to $378.44 for the Maxima sedan. A replacement key for the Volkswagen Golf will cost $370 plus GST. Ford charges between $60 and $250. Kia lists its keys from $21.37 to $281.20. Peugeot keys range in price from $330 to $678. The cheaper key needs to be cut locally; the dearer unit is pre-cut at the French factory and its electronics contain the vehicle identification number.

Chrysler keys range from $315 to $389. They use an electronic function to lock and start the car, rather than the blade and coded key in the Peugeot.

Such keys use similar technology: An electromagnetic field lights up microcircuits inside the key body, which broadcast a unique binary code to the vehicle's main computer, or ECU. When the ECU determines that the coded key is both current and valid, it tells the engine to start.

A BMW replacement key has the initial codes loaded to match that specific car's immobiliser. Each new BMW comes with 10 keys - three with the car and seven replacements. The 10 codes are stored on a database.

The replacement key will only ever work on the specified car. Keys cannot be replaced at a local level because the immobiliser codes are known only to BMW. But BMW New Zealand says keys can usually be replaced within a week.

Dumper agrees that the cost of keys is sometimes quite frightening.

"But the reality is that technology has delivered us a much more secure device, certainly in comparison with the house front door key," he says. "If you can appreciate how much technology goes into a cellphone, imagine how much you can fit into a car key that must also be secure.

"Unlike a phone that you can change from one sim card to another, each key must be unique."