Subaru Ej20 Wiring Diagram - MAPECU, MAPECU2 & MAPECU3 Wiring Diagrams. Below are a selection of MAPECU wiring diagrams for a wide range of vehicles, in alphabetical order. All MAPECU wiring diagrams are in PDF format and will open in a new window when you click on the name.. mark Reply: March 18th, 2009 at 2:40 am. Ken, thanks for your,s and Erics help . It appears that the manuals are for the 2.2ltr and 2.5ltr engines and my engine is a 2ltr.. Go easy on the subaru, it served you well, better than a volkswagen bug for a 4H design the heads are outboard and a unique design. This isn't a chevy 3500 we got here this is a scientific instrument, this engine- Yes, they are a bit fragile but pretty clever in a Japanese sort of way (no leg room)..