Locksmith guide
What to Do if You Lose Your Only Car Key
By Johnson Locksmith Inc. ·
Losing every key is a different and more expensive job than losing a spare, because the immobiliser has to be approached with no existing credential. An automotive locksmith can normally do it at your vehicle, but it takes longer, and several manufacturers impose a deliberate security wait period during the procedure.
First, check three places
It is worth two minutes before booking anything, because a surprising share of all keys lost calls turn out to be a key that was never lost.
Check whether a second key exists somewhere you have stopped thinking about: a partner's bag, a kitchen drawer, a previous owner's envelope in the glovebox paperwork, or with the dealership if the car was bought used and only one key was handed over.
Check whether the key is locked inside the vehicle rather than genuinely gone. If you can see it through the glass, this is a lockout and not a key replacement, which is a very different price.
And if the car is leased or financed, check whether the leasing company holds a spare, because a good number do.
Why losing every key costs more
Modern vehicles have an immobiliser. The key carries a transponder chip that answers a cryptographic challenge, and if the answer is wrong the engine control unit will not permit fuel or spark. The starter turns the engine over and nothing happens.
When you still have one working key, the vehicle can be persuaded to accept a new one relatively easily, and on many cars there is an onboard procedure that uses the existing key to authorise it.
With no key at all, the immobiliser has to be approached with no credential. On some vehicles that means reading a module directly rather than working through the diagnostic port. And on a number of makes it triggers a deliberate security wait period, typically ten to thirty minutes and occasionally longer, during which nothing can be done but wait with the ignition on.
That wait is not the locksmith being slow. It is the manufacturer making a roadside theft impractical, and it applies to legitimate work exactly as it applies to anyone else.
What a locksmith needs from you
Cutting a key to a vehicle is precisely what a competent locksmith must refuse to do without evidence, so expect this to be thorough.
- Photo identification in your name.
- Proof the vehicle is yours: the permit, an insurance document, or a lease agreement. A company vehicle needs the employer to confirm.
- The vehicle identification number, visible at the base of the windscreen on the driver's side and on the door jamb sticker. The key code is derived from it.
- The make, model and year, and whether it has a turn key ignition or a push button start.
- Whether the car has been standing. Programming holds the ignition on for a long period, so a marginal battery is a real risk and a jump pack should come along.
Locksmith or dealership?
Both can do the work and the honest answer varies by vehicle.
| Automotive locksmith | Dealership | |
|---|---|---|
| Comes to the vehicle | Yes | No |
| Tow required | No | Usually, the car cannot be driven |
| Typical cost | Lower | Higher |
| Evenings and weekends | Yes | Rarely |
| Makes with restricted security access | Cannot always complete | Can |
| Very recent model years | Sometimes not yet supported | Supported |
The lesson worth acting on today
If you are currently driving on a single key, have a spare made now.
The price difference between adding a spare and an all keys lost job is large, and it is entirely avoidable. Adding a spare is a short appointment at a time of your choosing. Losing your only key is an expensive appointment at the worst possible time, usually in a car park, usually in the dark.
It is one of the very few pieces of advice in this trade where the cheapest option and the most convenient option are the same thing, and the only cost of following it is doing it before you need to.