It sounds like the vehicle speed sensor (VSS), has malfunctioned and not sending signal.
The VSS measures the transmission shaft rotation and sends that information to the ECM and that gets translated into the gauge as the speed that you see.
The VSS is located on the back of the transmission on the driver side (see diagram below).
Please let me know of any questions.
Images (Click to enlarge)
Thursday, October 21st, 2021 AT 1:28 PM