I would possibly work backwards, put earths at ecu etc and see which earth makes it start (if your convinced it is an earth fault)
When the van is in a starting condition, do you then get coms with srs module? Because if the non start coincides with non srs coms, it might be quicker to find what is missing to prevent it talking. mend what you can see as faulty first, it will probably help if not sort the non start,
Sparki.