D3 Automatic no coms

Finally bottomed the prob
No comms reported various module and to ECU
Pulled out wiring harness - there are two components. One goes to the auto trans plug and the other goes to the rear transmission case plugs. There is wide misconception - the TCU is inside the auto transmission by removing the sump pan. The Integrated transmission ecu is next to the main ecu and controls the transmission after the auto transmission.

I checked earths and supply volts in the harness, re did the canbus splice in the wiring. At the ends of the harness to the auto plug and the difficult connector under the ECU I checked out good supply and earth. Checking the canbus wires local to these there were problems.

There was no canbus out put from the TCU even tho there was supply and earth at the plug.
So pointing to TCU problem. Avoiding huge costs decided to attempt break into TCU whatever cost - nothing to lose. You can undo it I used clothes pegs a gap supports carefully opening it up- there are hidden clasps to release
Once opened up all is revealed - water corrosion of supply - see pics

Repaired and joy - fixed saved a lot

Useful information and pictures, may I ask what was the fix? Cleaning board/pins etc or replacement I presume

Thank you tyregeezer, to get me started I soldered in insulated wire to bridge the breaks. What a bad design all those copper bar conductors and water ingress or condensation - not good. Bonus is my EPB after much work was still showing yellow on the dash and now all clear.
Let me see if you can help on my next issue to solve. Engine HP fuel pump - has two valves pressure and volume as these valves must operate independently you might expect each supply separately - the wiring diagram shows them supplied from the ECM with a splice so they both have the same supply from the ECM. My de duction is that they are in fact controlled by independent earth returns from the ECM.
My issue is with no DTCs to correct both valves have no earth return with ignition on. There is no indication of immobiliser active and the engine cranks but no rail pressure (tank supply on good pressure)

So is it that the ECM needs a signal to open these earths? (Valves work with 12v test and earth to ECM is good)

Any ideas or is the ECM knackered? A circuit diagram of the ECM would be useful .

Since then I have wired in low watts lights into the valves so can see , When starter activates both Pressure and Volume valves get only 2.6 v and i cannot see this being enough and consequently the cranking does not build rail pressure(gauge display)
I s the ECU waiting a signal to release full voltage? from somewhere.
I have spent an age sorting and clearing all dcs and only one remaining and may be pertinent- B1C57 Passive start ignition relay coil circuit.
Any ideas please