Hi I recent joined the mazda 2 owners club with my 2012 de 1.5l MX down spec. Much to my chagrin it developed clutch slip issue and I decided to fix it by buying a parts car and changing engine/gearbox over. Original pcm was used. All went well until the first start which saw a lumpy then high idle repeating for about thrity secs until shutting down with flashing secruity light on following restart attempts. No Crank no Comm..
Found ENG 10A indash fuse box blown and replaced it. When checking ENG INJ 15A and ENG BAR 15A in underhood fuse block touching them with test light connected to B- produced a buzzing noise which I found to be coming from the MAIN Relay. I changed this over with another but still No Crank no comm. Checked powers to relay, they are ok but no load side ground.
Diagrams I have are hopeless anyone know where the fuse box ground goes maybe I have forgotten to reconnect something?

 

Welcome to the forum