Not sure what fob is! But for the key, you need to approach the Mercedes Benz dealership. For the C240, 2002 model, I had to pay around $250 for a new key. It can open and close the door from around a block, so take care that you don't accidently open your car while handling your keys!
how to reset remote key fob for Mercedes SL 320
C200 key fob problem
No
Put the key in the ignition and turn the key 2 clicks to the On position and press and release the lock button on the fob. Then press and hold the unlock button on the fob 5 times and then release. This will reset the fob for your Mercedes.
Weak battery in fob?
To replace the battery on a Mercedes ml 350 key fob it is probably best to ask the supplier where it is purchased or there may be some instructions online.
check the battery in the car and the batteries for the fob key
get a new one :I lol
Take the metal key out of the fob and use it to press the button inside the key fob. That should release both side and enable you to open the key fob to change the batteries
I 7ih8 8. I78 8o8 8÷78
$250 @ MB according to forum
its like putting on a child safe lock or locking you glove box it a key you have to use the key to unlock it and the fob will work again.