Check your handbook. If it's a modern vehicle it might use the speedo as a diagnosis device. My motorcycle (YZF600R) uses the rev' counter (Tachometer) to alert the user of any faults in certain components eg: 3000 rpm = Throttle Position Sensor, 8000 rpm = Fuel Indicator Light.
So check the vehicle handbook/manual and you might get lucky.
Mr Smith
August 2010
It would be helpful to know what vehicle you are talking about Tony.
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