Right position rear light

Good afternoon is that any of you can help me? I have a problem with the right rear position I have changed the bulb but it doesn't work for me; also the fuses and everyone is fine; I have found that I have no current in that part.
The bulb has two resistance; one for the braking system and the other position; It is this that I have no current; What could I be?
Thanks for your collaboration. Jesus
the vehicle is a Ford Focus TDI 2003