Go to an open area.
Push the compass correction
switch, (the small (S) button next to the compass), holding it in for a
couple of seconds until the compass display first clears, then starts to
flash... let go of the button.
With the steering wheel on
full lock, drive the car slowly in a complete circle - this will reset
If you are unable to find a
large enough open area, complete the 360 degree manoeuvre slowly using
forward and reverse gears.
If this doesn't work, repeat
as above, but turn in the opposite direction.
If this still hasn't worked,
it's time to see a mechanic!