E87 LCI '07 N47 No power testing under hood

[dabp]

Had some issues with the battery over the winter, charged it with charger and it would start fine. Last week it didn't start again, just clicked and I assumed it was the battery again not holding it's charge(I never changed it in my ownership, had the car for 5 years). It would click like this if the battery was really flat, otherwise it would try to start and fail, so I sort of knew the symptom.

Fast forward, I go out and get a new battery, put it in today and it's the same, just a click from the enginebay. Got my multimeter out, battery is fine at 12.47V, however the two positive terminals located in the battery bay was really corroded, so took that apart, cleaned it, got new nuts and I assumed that was it, I measured 11.xV at the studs before clearning and 12.4xV after, so I assumed it was a bad connection, but no luck, still the same.

I went under the hood and measured at the hexagonal chassis stud and the positive tester thingymajigpoint next to it and 0V.


(Not my car, just for illustration)

So obviously something is wrong powerwise, but I don't exactly know where to start troubleshooting, any help would be greatly appreciated.


Also tested without IBS connected, no dice.