Buying a Used Car and the Extra Key Question

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Why the spare key deserves a question

Most of us look at mileage, tires, the paint and the way the engine sounds. Hardly anyone asks about the second key until they are standing in a parking lot a month later with one key in hand and a growing sense that they should have. The spare is not a luxury. It is the thing that saves you when the first one is lost, bent, run through the wash or locked inside the car.

A modern key is not a piece of cut brass anymore. Most cars built in the last couple of decades carry a small chip in the key head that talks to the car, and many have remote buttons as well. That makes a spare something that has to be cut, coded and sometimes programmed, which is a different job from copying a house key at a counter.

So the extra key question is really three questions in one. How many keys exist right now, are they all working keys, and what will it take to add another if there is only one? The seller can answer the first two on the spot, and you can plan around the third once you know. Our page on replacement car keys goes into the details.

What to ask the seller

Start simply. How many keys come with the car? Ask to see all of them, not just hear a number. A seller who says two may mean one key and one broken fob, or one working key and one old key that no longer matches. Hold each key, press each button, and note how the car responds.

Next, ask about the history. Has a key ever been lost or replaced? Was a key made after the car was bought? Has the car ever been rekeyed or had the ignition changed? Those answers tell you whether keys you receive match the current ignition, and whether any lost keys might still be floating around somewhere.

Finally, ask whether the seller has paperwork or a key code card. Some vehicles come with a card or tag that carries information used when a replacement key is made. It is not always there, but if it is, it can make a future key simpler. Do not worry if there is none. A trained technician can work from the car itself. If you are comparing offers from private sellers and dealers, our guide on how many keys come with a used car covers what is normal.

• How many keys exist, and can I see all of them today?
• Do the remote buttons work on each key?
• Has any key been lost, replaced or added since the seller bought the car?
• Was the ignition or lock ever replaced or rekeyed?
• Is there a key code card, tag or paperwork with the car?

Testing the keys you are handed

Do not trust a key because it looks right. Test it. Insert the key, turn it through every position, and start the engine. Then switch off, remove the key and try the other one. If the car starts with one and not the other, you have learned something useful that costs you nothing to learn on a test drive.

Pay attention to the remote functions too. Lock and unlock the doors from a distance. Try the trunk or hatch button. If the car has a push button start, check that it recognizes the fob with the fob inside the cabin and refuses to start with the fob outside. A dead battery explains some failures, but not all of them, and a key that works only sometimes may be a sign of internal wear.

Look at the physical key too. A worn key, with rounded edges and shallow cuts, may still turn the ignition but feel gritty, and it can wear the ignition cylinder sooner. If the key blade is bent or the plastic head is cracked, plan on replacement soon. Our page on key programming and fobs explains how remotes and chips are coded.

Transponder keys in plain language

Most cars from the last few decades use a transponder system. A small chip in the key head carries a coded number. When you turn the key or press the start button, the car sends out a weak signal, the chip answers with its number, and the engine control module compares it to the numbers it expects. If they match, the car allows the engine to start. If not, the engine may turn over and then shut off, or refuse to turn over at all.

This is why a copied key that merely looks right will not start the car. The metal blade can turn the ignition, but without the right chip the car stays asleep. It is also why a used car with a single working key is a mild problem and a car with none is a bigger one. Our column on what a transponder chip is walks through the idea in more detail.

The key point for a buyer is that a spare must be both cut and coded. Cutting alone gives you a door key. Coding makes the car accept it. Some cars let a technician add keys with the car's existing key present, while others need a specific procedure if all keys are lost. Knowing which situation you are in changes the plan.

There is a practical benefit to learning this before you buy. A buyer who knows the car needs a coded spare can budget time and effort for it, and a buyer who learns it at the last minute may feel pressured. Treat the key situation the way you would treat worn tires or a due service: not a reason to walk away by itself, but part of the true picture of what the car needs from its new owner.

What if there is only one key?

Then you have a decision, and it is better made calmly at the kitchen table than urgently at a trailhead. A single working key means you are one slip from a hard day. Misplace it, break it, or lock it in the car, and the cost and effort of getting back on the road go up.

The usual advice is to make a spare soon after buying. With the original key in hand, a technician can often cut and code a second one, because the car still has a key to learn from. Doing it before the first key is lost is a far simpler job than doing it after, when there is nothing to copy from.

You can also raise it with the seller. A seller who knows the car has only one key may be willing to adjust the price, or to have a spare made before sale. Rules and practices around what is owed on a sale vary, so ask a qualified adviser if you are unsure. Our page on cars and trucks describes the work we do for vehicles.

When the car has no working key at all

Sometimes a car turns up with no key whatsoever, perhaps from an estate sale, a long stored vehicle or a private deal that fell apart. This is the hardest case, though it is still solvable. A technician can generally make a key from the car itself, using the ignition and the vehicle's own information to cut and code a new one.

This process is called making a key from scratch or an all keys lost situation. It takes more time and more equipment than adding a spare, and the details depend on the vehicle. If you are considering such a car, ask a technician first whether the key can be made, and what is involved. Our column on making a key when you have none covers the basics.

One caution: a professional will want to confirm that you have the right to the vehicle before making a key. Expect to show paperwork that links you and the car. That is not a hurdle placed by any one company. It is how the trade protects owners from theft, and it is a good sign when someone asks.

Imagine you bought an older truck at an estate sale and discovered that no key came with it. You would be glad later that you asked a technician before paying, because the answer shapes the whole purchase. Some trucks are simple to key from the ignition. Others take more equipment. Asking in advance turns an unknown cost into a known one and keeps the surprise out of the driveway.

Remotes, fobs and push button start

Keys now come in several forms. A basic transponder key has a metal blade and a chip. A remote head key adds buttons on the head for locking and unlocking. A key fob with a hidden emergency blade is used with a push button start. A smart key lets you keep the fob in a pocket while the car senses it. The more features, the more there is to program.

Each of these can fail in a different way. The remote buttons can wear out while the chip still works. A fob battery can die. A blade can wear while the electronics remain fine. Knowing which part is dead tells you what has to be replaced, and sometimes only a battery is needed.

If a used car comes with fobs that act oddly, do not assume the worst. Try a fresh battery first. If the fob still misbehaves, bring it in for a diagnosis. Our guide on what to do when a key fob stops working offers a clear checklist.

Also check the emergency blade on a fob. Many push button cars hide a small metal key inside the fob that opens the driver door when the battery is dead. Slide it out and test it in the door lock. A blade that is missing, or that does not turn the lock, is a hidden problem that shows itself only on the day your battery dies, usually in a rainy parking lot.

Check the locks, not just the keys

A used car can have a tired lock cylinder even with perfect keys. Door locks, trunk locks and ignition cylinders wear with age and use. A key that goes in with resistance, turns with a sticky feel, or fails to release in the ignition tells you something about what is inside.

Test every lock you can. Try each door with the key, not just the remote. Try the trunk or hatch and the glove box if it has a lock. Turn the ignition several times and listen for grinding. If something sticks, ask for it to be addressed before you buy or plan for the cost afterward.

This matters more in a region with hot dry summers and, in the mountain towns, cold winters with ice. Dust and moisture work into locks and shorten their life. A lock that is stiff in the afternoon can freeze solid by morning. Our column on how weather affects locks explains the pattern.

If you drive up and down Interstate 5 or over to the mountain towns, you pass through several climates in a single trip, and a car that has lived in one place for a long time may have locks that have never met the other. A seller who kept the car in a garage will usually have gentler wear than one who parked outdoors beside a dusty lot. Ask where the car lived, and weigh the locks accordingly.

Safety and ownership questions

A used car comes with a history, and some of it follows the keys. Previous owners may have had copies made, and a key you never see could still work. If the seller cannot account for every key, consider whether you are comfortable with that. In some cases, a technician can change the car's stored key list so older keys stop working.

This is not a worry for most buyers, but it deserves a thought if you are buying privately and the history is thin. The car's computer holds a list of accepted keys, and a technician with the right equipment may be able to erase the old list and teach it only the keys you hold. Ask what is possible for your car before you decide it is needed.

Paperwork matters too. Make sure the title and registration match the seller, and keep any key related papers the seller offers. Rules about transfers vary, and this page cannot give legal advice. A local office or qualified adviser can explain what applies to your sale.

Planning the spare and finding help

The cleanest plan is to treat a spare as part of the purchase. Settle the key question before you sign, test every key, and schedule a spare soon after. Put the new key somewhere safe and different from where the first one lives. A spare left in a drawer at home is more useful than one hidden on the car.

Redding Mobile Locksmith serves seventeen communities across Shasta County and Siskiyou County with a branded service van that carries key cutting and programming equipment. The team works around the clock, which helps if a key problem shows up on a weekend. Use the request form to describe your car, since the phone line is coming soon.

Tell us the make, model and year, how many keys you have, and whether any are working. If you are near Redding, Anderson or Yreka, those local pages describe the area, and our page on locked out of your car may help if you ever end up on the wrong side of a door.

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