Well a new battery is definitely in order, but even if the battery was bad, with a jump, it should be able to still crank the x.

Take all the load you can off the X Meaning turn the headlight off, radio off, HVAC off, everything.

If that still doesnt do it. Your going to have to get under the X, locate the starter and tap it to move the brushes around. Doing so will place the contacts in a slightly different spot and i that is the problem, will start the X.

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2011 E70 50i M Sport