Check that the ABS is in proper working order
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.
Read the fault codes.
Test drive the car and check whether the ABS warning light goes out.
Check whether any fault codes have been generated.