My son recently purchased a 92 bmw 525i. The driver's side door will not consistently unlock, either with the key or from the inside. The battery was replaced shortly before he purchased the car and someone told me this may have reset some kind of security feature and the car simply does not recognize the key and therefor will not unlock the car. Does this make sense to those of you who know more about BMW's? If so, how do I get teh system reset to recognize the key?