PCM not foolproof Archives - Transmission Digest
An ASE Quiz (Not an Official ASE Test Question)

A 1998 Mustang GT shifts good through all gears and has converter lockup, but the speedometer is dropping out after driving a short distance. The scan tool shows that there is a VSS signal and reads correct speed when the speedometer drops out. There was a code in history for the VSS but after clearing it did not return.