Use this CANbus Pass-Through when installing our CANsmart™ Controller to a Harley-Davidson Motorcycle that has an existing aftermarket accessory that also plugs into the diagnostic port. The cable splits the diagnostic port allowing both the CANsmart™ and a second accessory to be connected bikes CAN bus. What's In The Box? (x1) CANsmart™ Pass-Through for Harley Davidson Fitment Note: Wiring Adapter - CANsmart™ Pass-Through for Harley-Davidson is compatible " ONLY" with older Harley CANsmarts that use the black, flat 4-pin adapter.