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451 Key Resync

Mod Details
PremiumNo Difficulty Mod ID1643 Creditevilution For451 Fortwo Link Copy to Clipboard


I found that if you don’t use one of your 451 keys for a long time and the battery runs out, when you refit a new battery, you may find that the key still won’t unlock the central locking.

Fault Or Security Feature?

Unknown but at a guess, I would say it’s a security feature. It could be if you lose a key, it automatically unregisters the key in case someone finds it and tries to use it to unlock the car.

Sounds Like A Pointless Feature

Agreed. If you used the manual key hole to gain access to the car, the blade will still turn the ignition and the immobilser chip will still unlock the immobiliser. Maybe it’s just to stop people from randomly walking around trying to find the car that it fits.

I’m clutching at straws for a reason why it happens.

What’s The Fix?

It’s something I found by accident. My spare key didn’t unlock the central locking but would allow the car to start. Even after replacing the battery with a new one, it still didn’t open the central locking. No beeps, no indicators flashing, no solenoid clunk and no relay click.

In the confusion, I put the duff key into the ignition and turned it to position 1. I then pressed and held the unlock button. A few seconds later there was a beep from the SAM unit. I turned off the ignition, removed the key and the buttons began to work correctly.

So it looks like it’s a way to reinstate the key back onto the system.

If holding the unlock button doesn’t, try holding the lock button. I wasn’t super paying attention when I did it but I’m sure it was the unlock button.