51 21 003 Replacing door detent (lock striker), front left or right

Release screws (1) and remove door detent (2).

Installation note: 

If necessary, carry out basic adjustment by way of notches (3) on door detent (2) and B-pillar.

Tightening torque 51 21 2AZ .

After installation: 

Adjust door detent. See 51 21 004 ADJUSTING FRONT LEFT OR RIGHT LOCK STRIKER  and 41 51... ADJUSTING LEFT OR RIGHT DOOR .

Fig 1: Identifying Door Detent And Screws

Courtesy of BMW OF NORTH AMERICA, INC.