WARNING: This page is about a different car, the 2004 Volvo S40, 2003 Volvo S40, 2002 Volvo S40, 2001 Volvo S40, and 2000 Volvo S40. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Identifying Pin Housing Opening
Courtesy of VOLVO CARS OF NORTH AMERICA.
First remove the pin housing from the outer shell.
Open the pin housing secondary locking by turning the two rings as shown. A "click" indicates that the secondary locking has disengaged.