Key for '96 W210
Thats the same part number as the key for my '97 E320 so I believe you are correct. Are you certain that the battery in the key is not bad or weak? This can keep the key from activating the locking system. Also, try all three sensors on the car - the driver door, the back of the rear-view mirror and the trunk lock. if none work and the battery in the key is fine, then there is something wrong in the guts of the system.