I bought a 2013 Q7 with the trailer hitch pre-wired without the hitch. I had the hitch installed by the dealer. Right after the installation and for four years later I did not verify the wiring harness if it was working or not. I guess I trusted the dealer. Now I need to use the hitch and the connector (Pollak brand) doesn't work. The car's manual says, the trailer's operation mode must be activated for the connector to work. But the book doesn't show or explain how it is done. I can't take it back to the dealer cause the warranty already expired besides I already spent $1,475 for the installation. I believe the dealer did not activate the trailer hitch operation mode for some reason. I never use the trailer hitch and the connector since it was installed, what could have caused the failure. Is there anybody who is aware of the cars software version that cover the towing operation mode?