The speedo takes its signal from the front left ABS sensor, so that info helps narrow it down.
80% probability the reluctor ring on the front left (passenger side) wheel is badly rusted, cracked or has fallen off. Visual check.
15% chance it's the ABS sensor on the front left has failed or is not correctly fitted. Visual check/test resistance.
5% chance it's a faulty/loose plug or damaged wire on the front left sensor. check visually/test continuity and resistance from multiplug at ABS controller to sensor.
vaux, February 2010
