From the Ford shop manual:

Continuous Memory DTC 512 indicates the PCM has experienced a power interrupt in its Keep Alive Memory (KAM) circuit.

NOTE:
If KAPWR is interrupted to the PCM, for example when installing a breakout box, or when battery is disconnected, DTC 512 may be stored in Continuous Memory.

Key off.
Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.
Install breakout box, leave PCM disconnected.
Measure voltage between Test Pin 1 and Test Pin 40 or 60 at the breakout box.
While observing DVOM, grasp the EEC-IV harness and wiggle, shake or bend a small section while working from the PCM to the dash panel.
Does DVOM indicate less than 10.5 volts?

Click here for a wiring diagram of the 1994 PCM KLM.

In other words you are losing power to pin one of the PCM. Check your wiring to pin one of the PCM.