if it helps when i fitted my rns 510 i had to change the wires round for the aux port due to this problem. if you look at the wiring diagram on the top of the rns 510 unit it tell you which connectors are for the aux port, check the wiring in the car is actually going to the right connectors, you can pull apart the wiring blocks and change the wires around to get it working, sounds hard but is easy