Ballast resistor wiring

I think as I said to Halifaxhops, there is a lot of tape wrapped and cable wrapped bundles in the engine bay and it would probably pay me to unbundle these in order to trace the circuits I want to test all the way to the bulkhead connectors etc, as you say don’t discount anything, there could be splices etc I can’t even see. Also perhaps it’s a chance to clean or replace the connectors, certainly the contacts in the ECM looked quite oxidised when I checked them earlier.