[Richard Crowley]

wrote ...
The cell phone that has the camera and a usb headphone is the Philips
Xenium 9@9R cell phone.
Yes, I am trying to connect it's usb output to a aux 3.5mm input of my
car radio. The cell phone came with a set of ear phones that plugs
into the cell's usb connector, but I want to drive a 3.5mm plug
instead of the headphones.

The 3.5mm plug Im using has 3 conductive areas (sleeve, ring, right,
ring, and left (tip)), yet the cable only has 2 wires (left and
tip)! Im not sure where this cable came from, but it had a 3.5mm
plug on both ends, so I just chopped off one end so that I could
solder it in place of the headphones. Perhaps this is an oddball
cable? If I find and cut open another audio cable (with 3.5mm plugs
on both ends) is it likely it will have 3 wires?

The little board in the case, has silkscreen that shows "L", "R" and
"GND", which is where the earbud wires were connected to, so Im pretty
sure thats correct. My only guess on why this isnt working is is that
plug's ground needs to be grounded with the board's ground. Is there
any other explanation?

Even if the Left and Right were reversed, what that cause issues?

So, to review the bidding:
1) you have a cable with a stereo 3.5m connector,
but only two wires in the cable.
2) You don't know which two parts (tip, ring, sleeve)
of the connector your two wires go to.
3) You connected your two unknown wires to L & R
and with the ground unconnected.

1) You almost certainly don't have the cable you need.
2) You must establish how your cable is wired if you
want to use it. (NOTE: If you get any other pre-wired
cable you will need to do the same thing.)
3) Wiring anything to just the "L" and "R" is almost
guaranteed to produce your "tons of noise and very
low volume" Reason: you are only hearing the
*difference* between the "L" and "R" audio signals
because they are both referenced to ground which
you left disconnected.

Connect the "GND" to the sleeve of the 3.5mm stereo
mini-phone cable. Connect the "L" and "R" to the
tip and ring of the mini phone connector. Some of
your noise may also be coming from the problem
of not using a shielded wire, as well.

Note that if you are trying to turn your phone into
some sort of hands-free device in your car, prepare
to be disappointed because it is rarely that simple.