I thought my sensor died when suddenly my temp read 28°F. It turned out that I just plugged the air duct where the sensor is full of 28° snow.

I think the sensor enters from the right side of the air duct that goes from the grill to the brakes on the left side of the car; you should be able to see when you remove the air stream panel below the bumper, hopefully forward of the aluminum platre.

I like you never found the step by step but at least I found the part on realoem so I could figure out where it was.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)