I have a 2001 X5 with a factory hitch and the round seven blade plug connector. I also have a boat trailer with brakes which uses the 5th wire solenoid lockout when backing the trailer. The 5th wire is always at 12volts when the standard tranmission on my X5 is in reverse. It is connected to the backup light circuit. If you have an automatic transmission it may be connected differently. If so just run a wire from the backup light to the harness. Hope this helps.

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