The remote key won't open the door even, if it is held close to the door. After I manually opened the door, both indicators are on. So, I replaced the battery in the key. The same thing was happening. The car battery was replaced two days ago. What could be the problem? A few months ago, the car battery went dead, however at that time; it was replaced with an old one from another car (E class) and a few months after that this started happening. So, as explained above, I replaced key battery, car battery with new one, but two days after replacement of the car battery this started happening again.

 

Check fuse #8 on the panel in the trunk. If it's blown, and blows again, then you have a bad ATA (alarm) siren. If it's not blown, then you have an antenna amp problem and that's much more complicated/expensive to fix.

 

Thank you for your answer, it was fuse 8 after all. So, if it blows again, would it be OK to disconnect the siren? I searched forums and it sounds complicated - at least for me. Or would it be better to completely remove the siren? Thanks.

 

You can just unplug the siren. It's easy to unplug it once you have access. You need to (SAFELY!) lift the front passenger side, remove the tire, then remove the fender liner.