Volvo Repair: DSTC Service required, traction control system, volvo s80

Question
I have a Volvo S80. The DSTC service required is staying on in the dashboard.  Also, the symbol is now on.  What does it mean?

Answer
  It means you are having a fault in either your traction control system, stability control system or the braking/ABS system. You will need to have the system scanned to indicate where the problem lies. Most common problem would be a wheel speed sensor.
  I wish people would read their owner's manuals.VBG

Mark