my 03 e240 has developed a locking problem with the front passanger door. when i press to lock or open the doors all the doors work ok except the f/p door. the interior button goes up and down several times at quick speed but does not lock. anybody any ideas? thanks

 

Most likely you have a faulty actuator located in the door.

Easy test is to swap over the yellow leads on the PSE and see if the fault persists on the same door or swaps to another door.
This test is easier than removing the door furniture changing the latch (tricky) etc because it COULD be the PSE unit in the trunk that is faulty (dependent upon model etc.)
Some have individually controlled outlets, others use shared single control port.

Stuart

 

E240 2004 left front passenger door wont lock at times doors wont open from inside when pulling door handle and unlock button on console has to be used

 

Merc E240 2004 left passenger door wont lock. At times all doors wont open from inside when door handle is pulled and unlock button on console has to be pressed to open