Correct, you can just hand remove the fuse panel cover and the 4 pin adapter is there.

There may be safety concern to just put the P2 control in the rear trunk: There is manual break feature in the controller, it may be required by law this feature is accessable all the time.

Prodigy uses accelerometer to engage the breaks, the device need to be mounted as instructed.

You can read the votage on the controler while breaking, it's obvious whether it works or not. If you put it in the trunk, you may not know at all if it's malfunctioning.

I would highly suggest to do it in regular way.

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2012 X5 35i: Hitch installed; Coded;