Here are some valuable pieces of information which helped me to learn a lot about my Ford vehicle electronic brain. Technical notes on EEC IV MCU (80 pages PDF document) Miscellaneous EEC IV info (diagnostic codes, wiring, etc) EECSucka - a ROM dumper for the EEC-IV (schematics, DOS executable) Intel 8061 assembler (Win32 executable and C source code) Intel 8061 disassembler (Win32 executable and C source code, plus A9L ROM image layout) Classic A9L ROM image (Mustang 89-93, E9ZF-12A650-AA) Calibration info (A9L, J4J1,  U4P0,  X3Z) EEC IV simulator -- runs ROM images on a PC ;)

The EEC IV Bible by Charles O. Probst:

This is how these beasts typically look like: