Heating the crimping sleeve
WARNING: This page is about a different car, the 2002 Volvo C70, 2001 Volvo C70, 2000 Volvo C70, 1999 Volvo C70, and 1998 Volvo C70. However, it is still accessible from the selected car via links, so may be relevant.
Hold a putty knife or other suitable protection behind the heat-shrink tubing to shield the surrounding components from heat.
Heat the sleeve with hot air gun: 9512777 and a suitable nozzle. It is important that the heat-shrink tubing is shrunk around the cable. It should be possible to see some adhesive that has squeezed out around the cable.