The is a fairly long list of causes that show the same symptoms so troubleshooting is necessary. I would start with reading for error codes. If there are codes write them down, clear them and see what codes return. Codes aren't always conclusive but they are directional. Reading codes will reduce the troubleshooting, getting to the core issue sooner and hopefully you won't be buying parts that don't fix the problem.

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