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.
Fig 1: Identifying Expansion Tank And Engine Coolant Level Sensor Connector
Courtesy of VOLVO CARS OF NORTH AMERICA.
Lift up the expansion tank and tip it to one side to access its underside.
Separate the connector.
Pull out and replace the engine coolant level sensor.