Central Door Locking System
Does the key start the car without problems?
If the answer is yes to both of those then the EIS ( electronic ignition system that generates drive authorization and unlock commands ) as well as the PSE pump and subsequent door actuators are okay. The guts of the fob are talking to EIS as well, which would indicate the optical IR ( infra red ) portion is working.
What is left is the path that the RF ( radio frequency ) from the fob takes to get to those control units. Which is from the fob to the antenna in back glass > antenna amplifier > overhead control panel > EIS > RCL ( remote central locking).
possible fault points:
1. RF transmitter in fob is dead. Remote trunk or alarm working?
2. antenna amplifier not working, How is your radio reception, trunk release and alarm ?
3. Antenna amplifier and overhead control panel not communicating. Any problems with overhead lights, sunroof or auto A/C temp settings ?
4. RCL is not getting authorization from EIS.
More info ...
http://www.benzworld.org/forums/w220...m-key-fob.html


