EDIT: pins #81,82 and 84 are used if you have an automatic transmission.
They are not used for my standard transmission.
However, you have ABS so your input/turbine speed sensor is not being used.
The ECU gets speed info from the ABS head unit if the car has ABS.
So the wires from pin #84 or #23 could be removed and used on pin #91.
Start with finding out if you have continuity along the full length of the orange wire, from the ECU to the sensor.
That orange wire also goes to both O2 sensors, the throttle position sensor, and the transaxle fluid temperature sensor.
Check that orange wire under your splice and see if you have continuity between it and the metal case of the ECU or body ground.
The wire may be shorted to ground.
It is a ground wire but it is supposed to be isolated from body ground and the signal may be lost if it touches body ground.
Look in the little hole on pin #91(the orange wire) to see if there is any obvious signs of damage to the metal tab by comparing it to the others around it.