Electronics schematics for engine bay

[vajper]

Where can I find the electronics schematics for the engine bay for a D3 4.2 TDI? More specifically, I'd like to understand what the signals are for the EGR valves (I have my guesses) but also where this cable goes?

Is it the ECUs which directly control the EGRs or can I access "the other end" of the cables to measure for continuity?

My problem is an intermittently working EGR where swapping EGRs doesn't solve the problem. I'm just hoping there is a problem with the cables...