2001 Voyager Speedometer failed

Hi all,

The speedometer on our 2001 Grand Voyager (3L V6) has stopped working.
The odometer is still counting, the speedo needle moves up from the rest
position to zero when the car is powered up, all of the other
instruments (rev counter, fuel, temperature etc.) all appear to be
working fine. There are no warning lights on, checking with a code
reader gives no stored error codes. I was hoping that the code reader
would give the road speed under live data, but that doesn't appear to be
supported on this car :-(

Any idea what I should look for next?

Thanks,

Matt