It will throw a code if failed, drain all of that yellow coolant and refill with either Zerex G48 or BMW Blue.
Inspect the coolant lines leading to the turbo, they will fail and leak coolant. You may see some white residue or in some cases crystallization. If you have plastic T connections, replace them as soon as possible. If they're metal, inspect the rubber lines and replace if necessary. Otherwise, if obvious leaks are not visible, connect a pressure fitting and set to 15psi and check again for leaks. You may need to remove the upper core support bar, it's just a few bolts but will allow for a better view.
