Ok here’s the first for me,,,check engine light on a 2016 F15 X5 PHEV,,,,the fault was electric auxiliary heater internal fault detected,,,performed the normal test operation. This is a pretty basic unit you have water in and water out,,,,you have a temperature sensor and a high voltage connection. After I decided to replace the electric auxiliary heater unit I had to find out where it is on the car,,,,found the unit under the car under the drivers side seat area,,,,removed the fiber board lower cover and found the unit,,,,but first you have to shut off the high voltage,,,this was a easy replacement disconnect coolant hose and 2 connections,,,,,add coolant bleed the system took some time.