SOLVED: X6 -N54 - Power but won't crank

[orgullodemexico]

This vehicle all at once decided not to turn over. Plenty of instrument lights, I could hear a click when pushing the start button, but engine won't turn over.

Connected a jumper cable from ground to the engine, and the car fired up.

After some inspection, I discovered two ground cables mounted on the passenger side inner fender that looked corroded. I wire brushed the connector plate and the cable terminals, reconnected and the engine fired. I disconnected everything to test my theory, and no start. Reconnected and the engine fired up

I'd like to know what both ground cables feed. One cable I identified on realoem.com as part # 12-42-7-574-962 "interference suppression band" What does the other cable feed?

I've read issues about the ground cable to the starter motor, but I'm without ability to lift the vehicle at this time but will pursue.

[lexkaz]

that is negative wire need to be connected to engine to run all electronics attached on them. DME unit uses mostly positive signal and negative come through common terminal.

starter has only has 1 positive cable attached and small wire for solenoid to push in.
negative wire get connected to engine -> body -> negative terminal of battery.