Another tool a home mechanic should have is a 12V probe. I have a Power Probe IV. It has great features. You have to be very careful using a 12V power source. I like to use to activate components. Two things are usually found. First, the part has failed. It won't power up. Second, either no power is going to it or a bad ground if found.

Have you checked pressure? Or put a vacuum on it?

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'06 X5 3.0i - bought @143,123 miles (12/26/20)