According to the interwebs, P115 is "Engine Coolant Temperature Sensor Circuit 1 Malfunction" (https://www.obd-codes.com/p01-codes). I'd start there. Make sure the sensor is reporting realistic values, i.e. ambient temp at cold start, slowly rising to operating temp of 80-110C (not sure what your vehicle normally goes to). If everything looks good, reset the code and see if it comes back.
I have found a few sources on the web that state P115C is a MAF code for BMW. It doesn't necessarily mean the sensor is bad, but it might be worth cleaning the MAF, clearing the code, and see if it comes back.
I've also found a list that doesn't have P115C, but does have P1151-P1159 and they're all related to the O2 sensors. If the code does come back, it may be worth checking your O2 sensors. How many miles on the car?