I just purchased a 02 W210 and it came with 2 keys. Both keys start the car fine - however - one of the keys does not work to lock/unlock the car (the remote or the blade).

Is there a way to re-sync the key with the car so that the remote lock/unlock works for the second key? It seems strange that it would start the car but not unlock the doors

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Daily Driver: 02 E430 4MATIC
In the family: '03 E500 // '04 ML500 // 64 220SE

Hello I would start by holding lock or unlock button on key down and look for an led to light at button area. If it dosent check the batteries first for 3v each. To remove batteries pull steel blade key and with same release button pull the center of key outward using that steel blade.
Otherwise if led dosent light the key is probably bad. Tim

Thanks I see the little LED and I don't see it lighting up. I'll try to replace the batteries later and see if that helps!

__________________
Daily Driver: 02 E430 4MATIC
In the family: '03 E500 // '04 ML500 // 64 220SE