Question: speedo question

[speed367]

My speedometer will only go up to 10 mph on my 93 vette. The fuel info is also off showing rang at about 12 miles when full. Is this a cluster issue or a speed sensor issue. Appreciate any advice.

 

[ecss]

If you have an oscilloscope it would be easy to verify where the problem is.

If you have a scan tool or scanner software does it display the MPH correctly?
That would tell you if the ECM is processing the VSS signal correctly.

If you have the C68 auto climate control press the up arrow and down arrow buttons on the HVAC control head fan control buttons at the same time. Hold them until you see -00 in the display.

This puts you in diagnostic mode. Press the up or down arrow until you see -07.
Press the button that is between the up and down buttons (I think the button is Auto). The MPH will be displayed in the LCD.

You can remove and examine the VSS driven gear. Verify the teeth are good. Attach a drill and spin the VSS.
Does the speedometer display over 10 mph? If it does the drive gear could be worn.

The output of the Vehicle speed sensor goes to the Selective Ride Control Module if you have fX3 (adjustable shocks) and the ECM which processes the signal into 4K pulses per mile.

That signal from the ECM goes to the Cruise control module. Does the cruise control work?
It also goes to the CCM which displays the speed and odometer on the LCD.
It also goes to the Radio Control head for speed compensation of the radio volume level.