I had planned to follow this guide to add an aux-in to my 3.0D Sport (build date 07/2001, with Nav & DSP) however I seem to have an issue. This part of the install, which details "... you can attach the other end to the spare connector on the back of the OBM unit. The module itself will plug into the factory/standard wiring harness and no additional work is required"



I'm assuming that the cable plugs into the back of the HU, but there's nowhere on the back of mine:



and I've checked the loom in the dash, and can't find anywhere along there either. I did notice that the HU in the guide has a different part number to mine (mines a tape deck too)



Any suggestions? Is it because mine's an early car? I've installed a few of these aux-in leads in the past (Z4, E46 M3) so I can usually find my way around these things.