BMW F30/F31 door lock faults
F31 driver's door won't open from inside or outside even though it is unlocked?
Usually the cause is a stuck or detached handle cable or lock mechanism. The repair requires removing the door panel to see the condition of the lock and cable. The mechanism can be treated with a suitable lubricant.
Why does a new lock body or cable make the door stick?
The outer handle cable may be too short or too tight, which holds the lock body jammed. Check the cable's length and mounting. If the fault returns, also check the door's position on its hinges.
What causes the rattle in the F30/F31 front door lock knob?
The nubs on the lock pin bushing wear, so the knob moves against the bushing and rattles. The new bushings can be replaced without removing the door panel. Padding placed inside the bushing also reduces the rattle.
Why won't the F31 door lock from the button, or the rear door won't open from inside?
A possible cause is a faulty lock actuator or lock motor. First check that the rear door's child lock is not on, because then the inner handle does not open the door.