Used Car Keys: What to Do After Buying a Car

Before you drive away: count and test what you were given

The right moment to sort out keys is the one in which the seller is still standing next to you. Ask how many keys the car originally had, and count how many you are actually holding. A car sold with one key when it left the factory with two is something worth noticing, not something to shrug about.

Test everything while the seller is present. Lock and unlock the doors with the fob and with the blade. Open the trunk, the fuel door if it has a lock, and the glovebox. Start the car with each key you have, and try the remote buttons from a short distance away. A key that fails the test today is a small conversation now, and a bigger one next week.

Note whether the fob buttons look worn, the case looks cracked, or the key feels loose. These are not reasons to refuse the car, but they help you plan. A worn fob is a candidate for a new shell or a new battery, and a loose blade can break unexpectedly.

Finally, write down the VIN and the key details while you are standing there. Those facts are useful whenever you call for key help later, and our page on what a VIN and proof of ownership mean for key work explains why.

If the seller is a dealership, ask directly whether the keys were checked and whether anything was done about previous keys during preparation. A straight answer, or an honest "I do not know", is useful either way. You are not accusing anyone, you are collecting facts so that you can decide what to do next.

The question nobody asks: who else has a key?

A previous owner may have kept a spare. A relative, a friend, a repair shop or a former employer could have had a copy cut. You cannot know. That does not mean anyone intends harm, but it does mean that the number of working keys in the world is not necessarily the number in your hand.

This matters more with a private sale than with a car that went through a dealer's preparation, and it can matter either way. If a dealer replaced or reset keys during reconditioning, they may have taken care of this already, but you should ask. Do not assume.

The question is not about trust. It is about control. A car whose keys you control is simpler to secure than one whose keys are scattered, and the earlier you deal with it, the less you have to worry about.

Some vehicles allow old keys to be removed from the car's memory when new ones are added, so that the old ones stop starting the engine. Whether that is possible depends on the vehicle, and we explain the options when you call with the make, model, year and VIN.

Think about the car's earlier life too. A vehicle that was shared among drivers, used for deliveries or kept at a business probably has had more keys cut than one owned by a single household. The more hands a car has passed through, the stronger the case for taking control of the keys.

Ask the seller about the paperwork and the spare

A good seller is often happy to hand over every key, the valet key if one exists, the owner's manual and any key code card that came with the car. Ask for those directly. If they are not available, ask where they might be and whether they could be sent.

Some cars come with a small card or tag showing a key code. That code can help a technician cut a new key accurately without needing the original. If the card is missing, there are often other routes, but having it makes things simpler. Our guide on key codes and duplicate keys explains what the code does.

If the seller says there was another key but cannot find it, ask them to look and to contact you if it turns up. A key in a drawer at the seller's house is a key you should know about, even if you decide not to chase it.

Keep a copy of the bill of sale and the title information somewhere safe. Ownership gets checked before keys are made, and having clear paperwork saves you from a delay on the day you need help.

If the owner's manual is missing, find the digital or printed version. It explains the key features, battery type, the location of any hidden keyhole and what dash messages mean. Having it saves guesses and also gives you words to use when you call for help.

Why one key is a risk, not just an inconvenience

A single key is a single point of failure. If it is lost, damaged or stolen, you are in an all keys lost situation, which is more involved than copying an existing key. It tends to take more steps, more checking and more specialist work.

With one key and an ordinary day, the risk seems abstract. Then the key falls out of a pocket at the beach, goes through the wash, or snaps in a stiff lock, and suddenly it is the only thing that matters. Our page on what an all keys lost situation means describes the difference.

Making a spare while the first key works is simpler than any alternative. The existing key can be tested, copied or used as a reference, and the pairing with the car is straightforward. It is the simplest form of peace of mind, in the sense of effort and worry.

If you have a household with several drivers, plan for more than one spare. Our guide on planning spare keys for a household helps you decide.

A final consideration is the cost of delay. Waiting until the only key is lost means doing more work in a worse situation, often at an inconvenient hour. Dealing with it now, while you can choose the time, tends to be calmer for everyone involved.

• Count the keys you received and compare with what the car should have.
• Test the doors, trunk, glovebox and ignition with each key.
• Ask about valet keys, key cards and code tags.
• Arrange a spare while one key still works.
• Keep proof of ownership where you can find it.

Check what type of key you actually have

Not all keys are alike. Some are plain metal blades. Some have a chip in the head that talks to the car. Some have remote buttons built in, and some are smart keys that let you start the car with a push of a button. What your car uses determines what a spare involves.

If you are not sure, take a look at the head. A thick plastic head often contains electronics. A flat key with no plastic probably does not. Our guide on smart keys, remote head keys and plain blades makes it easy to identify.

The key type affects what is needed to make a spare. A plain blade can be cut. A chip key needs pairing with the car. A smart key needs specific equipment. Availability and key type depend on the exact vehicle, so have the make, model, year and VIN ready when you call.

If the car came with a key that does not look original, perhaps one with a generic head or an odd chip, mention it. Aftermarket keys can work well, but they sometimes behave differently, and a technician should know what they are dealing with.

Look for aftermarket additions you did not expect

Used cars sometimes carry features that did not come from the factory. A remote starter, an aftermarket alarm, a tracking device or a modified fob may have been added by a previous owner. These can introduce extra keys or remotes that you may not have received.

If the car has a remote starter or an alarm, ask the seller for the controllers and instructions. A missing controller can mean features that you cannot operate, or a system that will behave oddly. Do not assume the seller remembered everything, and look for a small sticker or label that names the product.

Be careful with devices you do not recognise. If you find something under the dash or near the ignition that seems out of place, mention it to a qualified installer. We do not advise pulling wires or removing devices without knowing what they do.

If the car came from a rental, fleet or business owner, ask whether any tracking or management devices remain. These can be legitimate, but you should know what is on your car and who can see it.

If you find a device that appears to track the car or record data, you can ask the seller about it, or take it to an installer to learn what it is. You are entitled to know what is on your own vehicle, and sorting that out early avoids surprises.

Think about the door locks and the other keyed parts

A car may have more than one lock: doors, trunk, glovebox, fuel door, and sometimes a separate valet key lock. Keys may or may not be the same for all of them, depending on the vehicle. Test each one so you know what opens what.

A valet key is a limited version that can start the car and open the doors but not the trunk or glovebox, on cars that have one. If yours is missing, you can usually manage without it. If you did get one, keep it somewhere safe rather than in the car. Our page on valet keys and glovebox locks gives the background.

If any lock feels rough, stiff or worn, mention it early. A used car's door cylinders may have years of use, and a worn lock can wear a new key. It is better to know now than after the first break.

If a door lock has to be replaced or a cylinder changed, the new part can be set to work with your keys. Ask about that if it applies to your car.

Do not forget the small keys on the ring that came with the car, such as one for a trunk lock or a special compartment. Test those as well, and note which lock each one belongs to so that your spare plan includes them.

Fresh batteries and clean contacts

A used fob may have been running on its original battery for a long time. Replace it as a matter of routine, ideally with the exact type specified. That removes one variable and saves you from a surprise failure when the cell finally goes. Our guide on key fob battery replacement basics walks through the steps.

Clean the fob gently with a soft dry cloth. Wipe off grime from the buttons and the keyring area. Do not soak it, and do not use harsh chemicals. If the case is cracked, consider a new shell, which is a small job that keeps the electronics.

While you are at it, check the vehicle battery too. A weak battery in a used car can make locks and electronics behave strangely, and a fob can look faulty when the car is the real problem.

A short test drive, with the fob in several pockets and bags, tells you a lot about how the key behaves in real life. Do it before the novelty of the purchase wears off.

If you will keep a spare in the house, store it away from the car and away from anything with the car's address on it. A spare that is easy to find is easy for the wrong person to find as well, so choose a hiding place that only the household knows.

If you bought from a private seller, take extra care

In a private sale, nobody inspected the keys on your behalf. Treat the transaction as an opportunity to do it yourself. Verify that every key starts the car, that the fobs work, and that the number of keys you hold matches what the seller says.

Be careful with any seller who says the keys will be mailed later. Key delivery should happen at the time of purchase. Arrangements to send a key afterwards can leave you with a car you cannot secure and a seller you cannot reach.

If the title or registration is not in order, getting key work done may be delayed, because ownership has to be shown. Requirements for title and registration vary, so ask the relevant state office what applies to your purchase.

Keep a note of the seller's name and contact details along with the sale paperwork. If a question about keys arises later, you will want it.

A seller may sometimes be asked to provide a signed note stating how many keys were handed over. This is not required, but it helps if a question arises later about who held which key at the time of sale.

Plan the first week

Make a short list. Count keys. Test functions. Replace the fob battery. Arrange a spare while a working key exists. Decide whether to deal with old keys that might be out there. Do these in the first week, while the details are fresh.

If you discover that the car has only one key and it is worn, the sequence changes. Making a new key from a worn one can pass on the wear, so a technician may cut from a code or from the lock to produce a more accurate copy. Our guide on how worn keys affect locks explains why accuracy matters.

If you rely on the car for work or school runs, treat key planning as part of the purchase price in your mind. A used car with one key is not a bargain until the spare question is settled.

If you are not sure where to begin, call and describe the car. We will explain what is realistic for your vehicle, and our overview of car key services shows how we work.

Please bring every key you have to the appointment, working or not. Testing them against each other is how a technician learns which parts of the system are healthy and which are tired.

What to tell us when you call

Say that you recently bought the car, whether it was from a dealer or a private seller, and how many keys you have. Give the make, model, year and VIN, and mention whether the key is a plain blade, a chip key, a remote head or a smart key.

Tell us what you want: a spare, a replacement for a damaged key, or a way to make sure old keys no longer start the car. Each of these is a different job, and each has different requirements. Be ready to show identification and proof that the vehicle is yours.

We explain the work and the price before anything begins, and we test the finished work with you. If a technician cannot do something on your specific vehicle, they will say so clearly.

If you also need locks changed on a new home at the same time, see our guide on the moving day lock checklist.

Questions people ask