The ECT sensor says error - that means that either the sensor went bad or the HVAC unit cannot see it (wiring problem) - Its the engine coolant temperature sensor and is available quite easily too.

Its right next to the upper radiator pipe outlet on the engine and has an angled head.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)