I am trying to make bench harness for most newer GM ECMs. This is the information that I found here and in some other forums. I like to share it here with you so you can see that I am not just asking for help but contribute with something (altrough I just made a copy and pase):
E37:
Black Connector:
Pin Signal
8 Ground
19 Ignition
20 Battery
43 CAN +
44 CAN -
E78:
Blue connector:
J1-19=battery pos
J1-20=battery pos
J1-43=can low
J1-29=can high
J2-13=switched 12v+
J2-28=switched 12v+
J2-73= gnd
E39:
Blue connector:
J1-20= gnd
J1-30=gnd
J1-39=can high
J1-40=can low
J1-51=switched 12+
J1-52=battery pos
J1-71=switched 12+
J1-73=switched 12+
be sure to use a power supply rated for at least 3 amps as the e39 pulls a lot of current
E78 is the same as the mt-88, Entrol 88
we also put an led on the fuel pump relay pin to see if the cal is valid
E92 in attached image:
Attachment 21552