Alright, so, on the diesel D21 there is no super multiple junction; I added one by cutting the main harness at the driver's A-pillar, and splicing in a D22 SMJ connector, and used the QD32 engine room harness. The D21 cab earths are on the passenger's kick panel, and the driver's kick panel. No earth wiring runs through the SMJ; that would be a waste. My assumption was that the cab earth was duplicated by an earth in the engine bay, so I cut that earth wire on the cab side of the SMJ and terminated it in a tab beneath the driver's kick panel. I didn't realise that the earth wiring in the engine bay was common to the cab earthing, so what I had done was remove the main engine bay earth for the wiring harness. Because the starter, alternator, glow plugs etc use their own earth I didn't notice anything was wrong with the engine room harness. So the first earth I reinforced was the one I had created under the driver's kick panel. The earth that the lights had been using since I made the hybrid harness was the sensor wire earth on the passenger side wheel arch, which is about .01mm diameter, making the lights very dim and pathetic. To fix the problem I just broke into the harness where it vanishes into the quarter panel and found the fat black earth wire, and spliced in an OEM wire and tab and bolted the tab under the earth from the inlet manifold.