Turbo coolant pump issue?

So you found a bad ground it sounds like, good job. What is the code it has now, yes the change over valve gets is power from fuse #3 and it has a ground as the trigger. You can see it in the wiring diagram above. I would keep driving the car to see if the light clears and if not run the codes after driving it.

same code, didn't go away even after leaving the negative post disconnected while doing the job, soon as I connect it and start its there in the IDRIVE message drivetrain something I forgot ....same code 20A503, but u have to dig to find the code. That valve in the picture is not the changeover.

Okay, the change over valve is still tested with power and ground. The 20A503 code usually translates to: “Turbocharger coolant pump, self-diagnosis: signal implausible.” You must clear the codes, they will not clear having the battery disconnected.