OBD-1 flashing-lignt code 17 is for VSS.
OBD-2 scanner code P0500 is VSS for MT cars.
OBD-2 code P1791 is VSS for AT cars.

It may be that only certain cars ECU watches the VSS. For example without a VSS signal it won't engage VTEC; so maybe that means a non-VTEC ECU doesn't care whether the VSS is present or not? AT cars since maybe '94 use the VSS to decide shifting strategies.