Megasquirt schematics are copyrighted and are provided for existing customers to repair or modify their ECUs.
Most schematics are provided in the Hardware manual for your product. The following are additional ones that are not available within those PDFs.
V2.2 board (pdf)
Megasquirt 1 – V3.0 board
Megasquirt-1 external wiring diagrams
Microsquirt V1 metal case
Microsquirt V2 metal case
See your Hardware manual for external wiring diagrams.