i have a2001 mercedes slk 320 replaced batteries remote dosent work do i need to reprogram

Sad but you will have to go to dealer, or a shop that has the same tool, to get it reset. You only have about 60 seconds to get the new battery in before it loses all memory.

Make sure the batteries work first of all. Hold the IR portion of the key towards u & hold the button for about 1 second. You should see a red light flash once ( telling u there is juice in the batteries ).

You may have a loose contact within the key. If u give the key a gentle tap against the palm of ur hand it may knock the contact back into place & momentarily fix the key for you. If not, u can resynchronize FBS2 key with the car is remote entry control unit ( if l recall correctly ). Your owner is manual should tell u how to do it or just go to the dealer & ask them to do it.

If that does not work, u will need to order a new key. Those keys cannot be reprogrammed