Should not rise or fall if system has no leaks unless there is major change in temp or it sits for a lot longer than overnight. If you have adjustable height suspension you can see if it will change height. Or you can add weight and then turn on the ignition to see if the pump runs to compensate.

Is the warning coming on when you first start it or off and on when you are driving?

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas