Please help! I have a 2003 Fiesta LX. When I lock or unlock the driver door externally or internally, all doors but the passenger door do the same. However, if I lock or unlock the passenger door internally or externally all doors lock as they should. It is really annoying as it means when I lock via key fob, the passenger door doesn’t lock. So I have to go back to car and put key in passenger door. 
 

Does anyone have any clue what could be wrong? 

Could be a number of things, check "A" post connector contacts are clean and connector up tight, check connector on GEM,  and do this first.  Disconnecting the battery for 20mins is always an idea in case the GEM has got it's knickers in a twist.  Then you are into wiring, doorlocks or a hard GEM fault.  

Door lock problems on Fiesta/Fusions, are quite common, Good luck, and apologies for my sense of humour....

 

Think I leave it til another day🤣. I’m surprised I lasted this long without having the name mentioned in the group🤣🤣

On 9/2/2023 at 12:13 PM, Vaughanie0711 said:

Does anyone have any clue what could be wrong? 

Door locking motor/solenoid has failed in the passenger door. It may just be a broken wire or a corroded connection but you will have to remove the door card to investigate.

I have changed two door lock units in the front passenger doors in both our 2007 Fiesta and 2010 Fusion. (And in the Fiesta it had already been replaced !) All the door gubbins is in this one unit:

 

A pain to get at, I did find that removing the loud speaker makes the inner panel lighter and easier to manoeuvre, and a hole to get your hand in !

If you have got a dodgy lock motor, I would not deadlock the car (assuming you can on a 2003 model), as if the lock fails with the deadlocking set, opening that door will become very difficult.