The Fiero really has no computer control of any of its instruments.
The speedometer is run off of pulses supplied by the VSS, instead of a cable. The other gauges are fed by senders/sensors as they always have been.
They don't really start being controlled by a BCM until 1996, or thereabout. (The beginning of OBD2.)
The Fiero ECM is fairly primitive, in the grand scheme of things. Really all it controls is the fuel injection and ignition timing. (Of course there are inputs from other sensors, but that's what it all boils down to.)
Later ECMs/PCMs (starting around 1991) also controlled automatic tranny shift points.
[This message has been edited by Raydar (edited 10-28-2014).]