2002 Sierra Wiring

I'd like to patch into the aux of my factory radio/cd player.  I've done this with a 96 GMC Yukon by patching into the external tape deck sends.  Is the wiring similar? or did they make this easy with rca connectors on the rear of the radio?  It would be nice if i could patch this without taking my dash and radio off just to see if there are connectors.

anyone with experience with this truck or with a wiring diagram?

Thanks

There are no RCA's in the 2002 Sierra trucks  you will have to install a speaker to line level converter if you wish to add an amp. You can take the wires from the rear speakers or the wires going into the front doors at the boot.

The system in your truck should be almost identical to that in the Yukon:  main radio in the dash, auxillary player somewhere below, with a short cable connecting the two.

If you managed to accomplish this with the '96, then you obviously know what you're doing.  I'd start by eliminating any wires that are obviously NOT signal----first, test each wire to see if it's power, ground, or illumination---the rest of them must be data from the controlling unit, and music signal.

The '96 Yukon was relatively simple since there was already an external tape deck, so all i did was patch into the audio sends and pop in any cassette so that the radio would turn on the 'tape' signal.

I've taken the dash off my '02 Sierra and cd/radio out (rather easily) and there IS an empty plug for the external tape.  I've purchased the harness that plugs into this along with a wiring diagram.  I've isolated power, ground, illumination, RT audio, LF audio.  There are other wires, some at +12 volts and other that look like they are floating.  I've tried pulling some of these to +12 volts and ground, but the radio does not switch to aux.  I suspect that one of the wires (E&C Line) is a digital communication line but i may be wrong.  Any ideas?  Do some of these need to be at some other voltage rather than +12 volts?