I had the same problem. After buying 1 a new lock and 2 a new relay (yellow) at the passenger side (note: steering wheel is on the left), it turned out that the problem was the plug that wasn't properly inserted into the lock that was functioning WELL. A bit of yellow seal was still visible. Therefore, no signal was being sent back to the other door. A very stupid mistake, but it took me a few days to figure out because I kept looking for the fault in the non-responding door. Tip: the door trim comes off best when the door is locked, but for this you need to disconnect the battery's negative terminal and trick the door into thinking it's closed by pushing the lock with your fingers on the side where it normally falls onto the metal catch when it closes. Hope this will help