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Lost A Key

Mod Description
You lost 1 key? Not a big problem. You lost all of your keys? You are in trouble.
Mod Details
PremiumNo Difficulty Mod ID1026 Creditevilution For450 Fortwo451 Fortwo452 Roadster454 Forfour Link Copy to Clipboard

I Lost My Key!

Not a major problem, take your spare key and drive to your nearest
smart specialist and have them recode the car for a replacement key.

Err, 1 Problem, It was My Only Key

You're an idiot. Never buy a car with only 1 key and if you lose 1 of your 2 keys then get
a replacement immediately. Don't let that remaining key out of your sight and look after it.

If you bought a car with 1 key or some how lost both keys then you are about to agree with me that you're
an idiot. Get your wallet out because depending on the car, you could be spending a metric shit ton of money.

Fortwo 450 & Roadster

Have the car trailered/transported to a smart specialist or smart dealer and have them code 2, 3 or 4 new keys.
If you are only transporting a short distance and having 2 keys coded, you are looking about £350+.

Dealers can order the key blades already pre-cut for your car so you don't need a new ignition barrel.

Transportation – 2 new keys – TAN code – labour.

If you are too far from a smart specialist or dealer, the only other option you have is to send the
ECU and SAM/ZEE unit to a smart specialist for them to fit in another car and code keys to that.
They can then send your electricals back with the coded keys. If you can find a smart specialist
who can be bothered to do that it'll probably cost you about £400.

Secure postage to them – 2 new coded fobs – TAN code – lots of labour – secure postage back to you.

The obviously problem is the time it will take to send and receive these parts back. You will also
either need to order pre-cut key blades from smart or buy new blades and a matching ignition barrel.

Fortwo 451

To code a key on a 451, you need a key that has already been coded. It is known as a master.
Masters are set at the factory and replacements can be set as masters or left as standard keys.

If you have no keys then you CANNOT code new keys to the car using MB Star/Xentry.

Your only option is to have the car transported to a smart dealer and have them apply to smart GmbH for the password that allows their diagnostics to unlock the SAM unit to accept new keys. This is
to stop people from breaking into the car, coding a key they have with them, hot wiring the
ignition and driving away. This trick is easily possible with the 450 and Roadster.

At a guess, with a short transportation and 2 new keys, I'd estimate a bill nearing £500.

Transportation – SAM password – 2 new keys – TAN code – labour.

Dealers can order the key blades already pre-cut for your car so you don't need a new ignition barrel.


Several companies offer mobile recoding of the immobiliser but it won't be cheap plus the keys they code
to the car will only disable the immobiliser, they won't have the buttons for central locking and you'll
have to fit a new ignition barrel. For all of this, you are probably looking in the region of £350.

Call out fee – excessive rates – 2 immobiliser only keys – new ignition barrel.

The other option is to transport the car to a smart specialist or smart dealer, have them order pre-cut keys, delete the old keys from the system and recode some new keys. This way you are looking at about £300 for a sort transportation and 2 keys that operate the central locking. Dealers can order the key blades already pre-cut for your car so you don't need a new ignition barrel.

Transport – 2 keys – TAN coding – labour.


Don't just have 1 key, EVER. If you lose a key, get it replaced straight away. It'll save you a lot of money.


It is important to remember 1 thing. The keys aren't the parts that are coded.
The CAR is coded to work with the new keys, that is why the car has to be present for coding.

You CANNOT code keys to work with your car, it doesn't work that way around.

All the keys you want coded have to be coded at the same time. You cannot add to the system.