Here are a couple of pics. The unknown wire is the one with the circle connector. that comes out of the harness that goes into the ecu box
I bought a 330ci that had been in a minor accident (front end). I was told the fuel pump needed replacing and I did so. There is no power to the new pump and it cranks, no start. I checked fuse in ECU box and changed relay. The main code I get is 50B - MRS battery positive terminal isolation 1 and MRS power supply.