WTF is up with my Radio

[MoVolvos]

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Probably sold more AUX units than W/O AUX. The above maybe refurbed units also as it says Exchange.

[mrbrian200]

As far as the reverse sensor function, there may be a software component involved. If the used radio came off a vehicle that did not have the reverse sensors installed they may not work properly. This might be a downloadable package that is updated/installed at a dealer/VIDA. I seem to recall the 'parts list' for dealer added reverse sensors included more than one software download. One of them likely is applied to the ICM/AUM (radio) to make it work properly with the reverse sensor system.

[Gritty]

Maybe I wasn't clear...
On my old HU-650, there was an AUX source input, along with FM1, FM2, FM3, CD, Serius XM, etc...
On my new (used) HU-650, AUX does not show up with all the other Sources.
I reinstalled all the harnesses and cables into the identical slots that they came from. I'm not sure which one was the AUX cable, but it shouldn't matter.
I'm wondering if there is a way to enable the AUX source on the newly installed head unit.

Nope, crystal clear. I also was having issues in a 2007 V70: random input changes from (for example) FM to AUX when going over bumps. Then a whine developed on the passenger side tweeter. Sounded at times like a steady whine, at times like a 56k modem connecting. Replaced HU 650 head unit with a HU 650 head unit. Whine is gone (and CD works for the first time ever) but NO AUX. No more MP3s. Not sure about back up beep.

Would be nice if there is some magic code or secret handshake (I.e "press and hold these two buttons for ten seconds") to get AUX back. Getting at the unit was a bitch.