You only really need to worry about the supply and earths initially.

Connector A
Terminal
D1=battery volts ignition on
L1=earth
M1=earth

Connector B
Terminal
L1=earth
M1=earth
M2=battery voltage(ignition on and or cranking I'm not sure, possibly cranking only as it feeds injectors)

Connector C
Terminal
D1=battery voltage on AD, relay switch on Peters.
G4=earth
H1=earth
H4=earth

Check these and report back.
Might be a good Idea to check supply and earth at diagnostic socket too, in case it's a main vehicly supply or earth