So I’m having what I think is a unique problem. The key fob lock and unlock are not working. I’ve replaced the battery’s. I’ve tried disconnecting the battery. When I do that the key fob works to lock and unlock the car just fine. Then I try it again later and it doesn’t work. I’ve tried re syncing the fob with the car by double pressing one of the buttons and then turning the car on and that also works at first then also stops working later in the day. The car starts and unlocks fine with the key so I know it’s not the locking mechanism or the skeem. Any ideas on how to resolve this issue would be appreciated. We have only had the car a couple of weeks so I may not be up to speed on how to resolve this yet or what it might be causing the issue. When I re sync the fob inside the car the flashers blink twice then I insert key and turn to on position. Not sure if I’m just doing something wrong on the process of if something is faulty. Thanks for any help.

 

Do you only have one key?

 

Two keys one key fob

 

When you disconnected the battery you reset the PCM and thus initiated another period for the car to find and code an error. It seems the car is turning the locking system off because it sense a problem and so you should be able to find a Diagnostic Trouble Code. Hook up a scan tool and see what the DTC is. Get the exact number, not some explanation from who ever hooked up the scan tool. Some codes are not available to the less expensive tools, so you may have to go to a garage that specializes in Mercedes to find the specific code. It is best to get a scanner for yourself if you haven't one already.

You should also check for water below the styrofoam that is under the carpet in the trunk.