How To Open Mercedes Key Fob 2005. You may be activating the door lock / unlock via the infra red signals from the key fobs to the driver's door handle receiver, or the trunk. Picture of plastic retainer that holds this cover in place.
That is the only way. If the key fob appears to be working, see if the remote is transmitting a signal. This is the most common thing i see at my shop.
I have to put the key and literally touch the door sensor for it to work.
It is possible for either component to fail exclusively of the other. If the red light on the key fob comes on when you press the lock/unlock button then the battery is fine. If the key still starts the vehicle, you now have a bad key fob. The key has two components to it.