iPod through aux on factory Delco stereo

[Mike Mercury]

My question is; has anyone removed their head unit and is there an 'aux' input in the rear of the unit?

there isn't (in the conventional audio way). The AUX input is indeed for the rear mount CD changer. On 1999 thru 2004 C5's there is a factory run harness from the rear of the radio to the passenger footwell. (There are reports of 1997 and early 1998 C5's not having this first harness installed.)

For those that ordered the factory CD changer, a secondary harness was installed and it plugged into the connectors found at the passenger footwell - and ran to the rear and plugged into the CD changer. If your C5 never had the optional CD changer, the second harness (from the footwell to the rear) was never installed at the factory.

In the harness going to the rear mount changer, there are a few wires.
*12v
*ground
*Audio - L
*Audio - R
*audio ground
*serial data line

the serial data line is used to send commands back-n-forth between the headunit and the CD changer. The changer also sends serial data to the headunit about the disk number and track number on this same wire.

the problem that most people run into trying to use the "AUX" input for something other than the factory CD changer - is that the radio won't activate the input unless it sees valid serial data coming from the CD changer.
There are aftermarket gizmos that connect to the changer harness. They send useless (but valid) serial data to the headunit - fooling it into believing there is a working factory CD changer connected; and the AUX input is activated.

I use the PIE GM10-AUX adapter for my hard drive based MP3 player. Here are pics of my Neo player:

remote control head is mounted in the center airduct (I already have a ham radio in the ash tray area... or I would of placed the MP3 player remote head there). And yes... the center duct still functions (but obviously somewhat restricted).

I mounted the main chassis where the optional factory CD changer would of been installed:

keep in mind that the PIE adapter only activates the AUX audio input on the head unit. You can't control the functions of your added audio device via the buttons on the factory radio. All that still functions are the Volume and tone controls when you're using the AUX input.

And the PIE adapter connects into the harness intended to plug into the CD changer. If you already have a CD changer... to use the PIE adapter you would have to diasble (unplug) your CD changer.

My 2002 was ordered without the rear mount CD changer. I purchased my MP3 unit, PIE adapter, and footwell-2-rear harness; and now have it playing (direct connected) through the factory headunit.