From ebay if I remember right. It is in OEM packaging. I'll update this post once I try the new cable.

The crux of my question really has to do with what level of effort and what materials are involved with installing an AUX cable. I haven't searched for a DIY yet so I don't know if there's a procedure posted. I presume you have to pull the radio and such. Not sure how complicated that is... Got a DIY for me?? :D

at the top of the page, there is a link to "how-to". click on it, go to X5 link, the AUX info is there...

thanks for this info.
I performed this mod years ago but without soldering the 300k ohm resistor i place, but just wrapped tightly around the metal connections (removed the pins from black plastic housings) but over time it must have loosened as it was intermittently working.

My e53 uses the B1 connection at the black plastic housing.

I was at a pick-n-pull and grabbed an e46 OE Aux cable...and upon comparing, the same three wires exist but with a different black plastic housing connector and different pinlayout location (but same shape pins).
I rewired this e46 cable to the e53's connection plastic housing for B1 and upon hooking it up, still no fix...

So, i removed the fabric tape off the e53's inline motherboard to see if there was a crack in any solder but nope. so i tested the resistor with a multi-meter and its value settled in at 297k ohms.
perhaps this wasnt enough to trigger the AUX feature.
so i soldered a 300k ohm resistor by the black plastic housing between the white with red stripe and white with blue stripes. i connected it into vehicle and this time its perfect again.

SO, idecided to add the same resistor to the other e46 cable I have, too, so its a back-up :)

all thanks to this diagram you supplied in post 6. cheers
https://uploads.tapatalk-cdn.com/202...b2ad5cedb7.jpghttps://uploads.tapatalk-cdn.com/202...22fbebf544.jpg

Resistors are usually either 1% or 5% tolerance, so 297k ohms is within tolerance for a 300k ohm resistor... just sayin' ;)

I agree, but for some reason, the resistor buiilt inline was not triggering the AUX feature anymore, until I soldered in my own 300k ohm resistor, too. odd.