How about this from the Fiero On-Line Service Guide?
My computer won't flash any codes. Could there be a bad connection somewhere, or is the computer shot?"
The computer should flash a 1-2 code three times before and after any stored trouble codes. Since yours does not, I'll put my money on a bad computer.
However try this to make sure:
Remove the connector (it was a white connector in 84) from the computer. The Check engine light should go off. If it does not, there is a short on the wire leading to the light. Fix the short and don't read on
Reconnect the ECM connectors. Make sure there is a good ground to the diagnostic terminal (B). You might also want to try putting a ground at the ECM connector wired to terminal (B) (white connector pin #3 in 84). If either of these gets you a 1-2 code, your computer is good, but the wiring ECM to diagnostic gounding terminal A or bad wiring from ECM to terminal B.
If all this fails to give you a 1-2 code, open the ECM and carefully remove the PROM. Be careful not to bend the pins, and remember which way it was installed.
Make sure the ignition is _OFF_ before you remove the PROM.
After the PROM is out, turn on the key, ground the diagnostic terminal and look for a 5-1 code. If you get the 5-1, you need a new PROM, it not, you need a new ECM box. However, you should check for low resistance between the ECM box and various solenoid terminals before replacing the ECM: TCC solenoid (if automatic), A/C relay (if equiped) and Cooling fan relay. If these measure less than 20 ohms, they will kill the new ECM box very quickly. If they all measure more than 20 ohms, just replace the box.
