Driving in town, stopped at a red light & all of a sudden, my ultraGauge beeped giving a message saying MPH warning showed 118 as the speed & gave a 90 MPH max statement. The Discovery acted like it was going to shut off, but the idle returned to normal. Anyone ever experienced this? I've had my speedo jump while sitting still before, but never got a warning.

 

The vehicle speed sensor is about to die. When it detects you approaching take off velocity, it cuts off spark and fuel to bring you back to reality. There is a good rebuild article on that around here with pix. You can unplug the sensor ( transfer case) and drive until repairs can be done. Sppedo won't work, use GPS.

 

As always, thanks for your input SB!! I did fond the rebuild thread you mentioned in the Tech Section & read it. Although I seemed pretty simple, I was unable to see how it would make the truck decide I was driving 118 MPH when I was sitting still as the shaft would be stationary too, right?? Guess it creates a short somehow... Will order a new one I guess.

 

The sensor is a magnetic switch, and the rotating part is a magnet. The nylon bushing wears out, allowing the magnet to wobble all over the place, even when the vehicle is standing still. each time it moves, it causes the sensor to send one pulse to the ECU, which converts that into speed readings.

It's also possible that the sensor itself has gone bad, but taking it out and rebuilding it is considerably cheaper than buying a new one.