Speedometer reading way off correct speed

Hi


Suddenly my speed reading appears completely wrong(20miles over correct speed)
No modification done, nore any service at the speed gear / reading unit.
Is it something wrong with the ECU?

Some ideas ?



(XJ 97, 4.0L Sport, Manual transm., NP 231 Transfer)

Anyone with some help ?

No idea.

Maybe it's confused. Did you try reseting the PCM by disconnecting the battery, then shorting the positive lead to ground, then reconnecting the battery?

The transducer at the back of the transfer case just counts revolutions.
I supose you could pull it and see if the gear looks OK.

-Ron