How to Identify Benz FBS3 vs FBS4 Key by Shell and PCB?

Here is the tip to identify if your Mercedes Benz BGA key is FBS3 or FBS4 by key shell and key circuit board.

1.By Key Shell

We can tell FBS3 or FBS4 from the key.

We can also determine whether it is an FBS3 or FBS4 key from this part of the key. Here is a string of numbers.

With a letter “K” means it’s a smart key, without “K” means semi-smart key.

3 numbers before this space indicate it’s an FBS3.5 semi-smart key.

4 numbers before this space indicate an FBS4 semi-smart key.

“K” at the beginning means it’s an FBS3 full keyless smart key.

“K” in the middle means FBS4 full keyless smart key.

2. By Key PCB

On the FBS4 key board, there is a transistor on the right side here; the FBS3 does not have one.
The chips on the FBS4 key board are smaller than those on the FBS3 key.

How to tell if it’s smart or semi-smart:
A full keyless smart key will have an extra accelerometer chip on the top right side; a semi-smart key does not.

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