Lost your car keys? How replacement and programming work.

What kind of key does your car use?

• Traditional metal keys: older vehicles. Cut only, no programming.
• Transponder keys: a chip in the head talks to the car's immobilizer. A key can be cut perfectly and still not start the car until it is programmed.
• Remote-head and flip keys: a transponder key with lock and unlock buttons built in.
• Smart keys and proximity fobs: for push-button start. The car detects the fob nearby, so it must be programmed to the vehicle.
• Laser-cut or high-security keys: a groove milled into the blade instead of notches on the edge. They need a specialized cutting machine.

Adding a spare versus all keys lost: what is the difference?

Adding a key while you still have a working one is the simpler job. The new key is cut and then programmed alongside the existing key.

All keys lost means there is no working key to copy. The key has to be cut from the vehicle's key code or by decoding the lock, then programmed to the immobilizer from scratch. It takes longer, but on most vehicles it can still be done where the car is parked.

Dealer or mobile locksmith?

A dealership can make a replacement key, but with all keys lost that usually means towing the car there, and some keys have to be ordered. A mobile automotive locksmith comes to the car and cuts and programs the key on site, typically without an appointment wait.

Some newer vehicles have restrictions on key programming. The fastest way to know for yours is to call with the year, make, and model before anyone heads out.

What do you need to have ready?

• Photo ID and the vehicle's registration or title, to prove ownership.
• The year, make, and model, and the VIN if you have it (it is on the dashboard at the base of the windshield).
• The exact location of the car.

Any tips to save time and money?

• Get a spare now. It is far simpler than an all-keys-lost job later.
• Be careful with cheap fobs sold online. Many are the wrong frequency or chip for your vehicle and cannot be programmed. Check compatibility first.
• Key broken in the ignition or door? Do not keep turning it. Broken pieces can usually be extracted and a new key cut.