What does the blade do on the FOB of a keyless car?

[Bazman67]

Hi there,

I managed to lose the blade off my key fob!

The car still starts thankfully, but I's still like to replace it (as cheaply as possible).

Can I take the blade from any f30 bmw and slot it straight in or is there something else I need to do?

Thanks

[edd344]

It's for when your fob dies in effect, so no, you'll need to get one that matches the door of your car else people would be walking round unlocking other peoples bmws...

[irocfan]

also needed for when/if your car battery dies

[De Sisti]

This video below explains:

https://youtu.be/UP7hmVLKyjA