[Moose Test]

To add to the good advice already given, I'd deal with the alternator problem first, as the electronics on these models are known to throw spurious errors when there are poor voltage conditions. Once that's sorted and you've cleared down existing DTCs, then what remains/recurs is 'real' and can be trusted as the basis of further diagnosis, if any is required.

That's the meaning of the "Power System Urgent" message, the CEM thinks the charging system has a fault. Possible causes may be that you have the wrong alternator fitted, or issues with the alternator wiring (either the power connections, including grounding leads) or the smaller connector which brings digital signaling into the alternator.