Mondeo mk4 central locking problem

Hi everyone looking for a bit of help with my mondeo 2012 2.0 tdci, il start from the begining ,basically unlocked car and drove to work as normal got out and went to lock the car and nothing ,no response when i press the lock button on the key (car is not a keyless entry model has a standard remote key fob with flip out blade to start car ). So iv been locking/ ulnocking car with key in door .

Iv got a spare key both keys are not working both batteries are good and keys have been tested and are emitting a signal, so pluged in snap-on scanner and retreived fault code U201F-87 external reciver message missing from the cars bsi , code is a current dtc and will not clear, i had a look at the fuse for the reciver this was ok and has battery voltage across it, so next step i found the reciver located in the headliner just behind the roof light , had a look at it and found the plug had gone all green and inside the receiver was green also so bought a brand new receiver from ford and replaced the green terminals in the plug , went to clear the code and it came straight back tried the key fob programme where you turn ignition on/off and listen for the beep which i get from the car but no corrosponding beep back to say it sees the key so i  checked fuse again thats fine checked voltages at plug at receiver and i get one 12v live on pin 3 which is the one that has the feed from fuse f14 5a in bcm, iv got earth on pin 2 but on pin 1 im getting another constant 12v feed ??? This is the comms wire between receiver and bcm so was  expecting to see between 0-5v which changes as the key fob button is pressed ???? Is this right ?? Has anyone had similar problems , i know the bcms are prone for doing weird and wonderfull things but want to confirm if its this at fault any ideas

Cheers guys all help apreciated