Bought a used car with only one key? Start here

What to do first: test the key, then add a second one

With one key, you're a single lost key away from a car you can't open or start. While it still works, have a spare made from it. That is usually a lighter job than making a key for a car with none, which is what all keys lost means.

Before you call, find out exactly what you're holding. Whether the car came from a lot on Fairview Avenue or a neighbor in Kuna, buyers often learn later that the key is missing something, or that the extra one in the glovebox never belonged to the car.

Check what came with the car

Sit in the driver's seat with the key and work through this list:

• Does it start the engine? A key that turns the door lock but won't start the car may be a plain copy with no working chip.
• Do all the buttons work? Try lock, unlock, trunk or liftgate, panic, and remote start if the car has it.
• Is it a valet key? Some models came with a key that runs the engine but won't open the glovebox or trunk. Your owner's manual will say whether yours had one.
• Is the hidden blade there? On a smart key, slide the release and check that the blade turns the door lock.
• Does the extra key really work by itself? Leave the main key inside the house, then try the second key alone, buttons and start. Many cars start when any recognized key is inside, so testing them side by side can fool you.

Look at the wear, too. Rounded blade edges, a split case or a button that needs a hard press say the key won't last, and it's easier to copy before it gets worse. Our chip key page explains why a copy made at a hardware-store machine often opens the door and then won't start a modern car.

Keys you don't have can still be out there

A used car may have picked up several keys over its life, and a former owner may still have one in a drawer. If that bothers you, there's something we can do.

On many vehicles, the locksmith can remove lost keys from the car's memory so they no longer start it. On a lot of cars that works by clearing the stored keys and adding back only the ones that are present, so bring every key you plan to keep.

Be clear about what erasing does. It stops the old key's chip and buttons from working with the car, so that key can't start the engine. If the missing key also has a metal blade, that blade is still cut to your door lock and could open a door by hand. Tell us what worries you on the call, and we'll explain what can be done for your vehicle.

Before you call: what we'll ask

These details let us explain the job on the phone:

• The year, make and model. The VIN on the registration helps too.
• Where the car is: your driveway, a work lot or a parking lot, with the nearest cross streets.
• The key you have, plus anything that came with it, such as a second fob that may or may not work.
• Whether you also want keys you don't have erased from the car.
• Your photo ID and the title or registration. If the paperwork from the sale is still being processed, tell us what you have.

The price is explained on the phone before anyone drives out. Tell us where the car is and we'll tell you when we can be there. If something different turns up at the car, such as a worn ignition, you hear about it and the new price before any extra work.

Which page fits your situation

If you have one working key, this guide and our spare car key page are the right place to start. If the only key is already gone, or it no longer starts the car, read all keys lost instead.

Thinking of ordering a fob online? Read whether an online fob can be programmed before you buy. Many can't, so we check compatibility first and promise nothing for third-party keys. For a car with a start button, see push-to-start smart keys.

Step by step

1. 1
   Paperwork checkThe locksmith checks your photo ID and the title or registration before making any key.
2. 2
   Look at your keyYour key is examined so the new one matches its blade and chip type.
3. 3
   Cut the new keyThe blade is cut on the key cutting machine that travels in the service vehicle.
4. 4
   Program it to the carThe new key is added to the car's memory, and missing keys are erased if you asked and the vehicle supports it.
5. 5
   Test every keyEach key, old and new, is tried on the locks, the buttons and the engine start before we leave.