The remote locking on my 1999 Focus has stopped working. I took the key to my local Ford dealer and had them fit a new battery to the key, but this has had no effect. Strangely all the doors unlock via the key successfully, so I don't think it's a fuse problem as such. Also the internal boot release button works. Does anyone know how to fix this? Is there a sensor that gets "dirty" and stops this from working? Thanks, Gary.