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Need help with deciphering the stereo wiring on my '90

Josh B.

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So after having an aftermarket stereo for over a year, I finally decided to tackle installing it. I'm tired of listening to music on my phone while driving lol

Hoo boy. I have a Kenwood CD/Bluetooth stereo, and a Scosche GM stereo wiring harness adapter (part no. GM02B, pictured toward the end). The adapter fits all four of the harness plugs that were plugged into the back of the factory non-Bose cassette/radio unit. (Unit is dead, probably bad capacitors. Might fix in the future, might not. I haven't owned cassettes in 20 years, so... yeah, hehe). I'm terrible at reading these types of wiring diagrams in the GM Repair Manual, but this is everything I've gathered so far.


What I believe I know (please correct me if I'm wrong):

White plug is the front speakers (TAN = Left+, GRAY = Left-, LT GREEN = Right+, DRK GREEN = Right-)
Blue plug is the rear speakers (BROWN = Left+, YELLOW = Left-, DRK BLUE = Right+, LT BLUE = Right-)




What I think I know (DEFINITELY correct me if I'm wrong):

The black 6-wire plug shown below has four wires. Yellow, Brown/White, Pink, and Black. I *think* the PINK wire is what raises and lowers the antenna? BLACK I assume is ground?


What I DEFINITELY don't know:

The YELLOW and BROWN/WHITE wires on the 6-wire plug. I can't tell if these are radio and/or CD(not equipped in mine), or if these are the power wires for battery+ (maybe Yellow since book says "HOT AT ALL TIMES"?) and accessory+ (Brown/White?). Really unsure. However, I hope they're the power because of the one major thing that concerned me with the fourth plug. The fourth plug (shown below) is a 7-wire plug with four wires. Black, Purple/White, Gray, Green. The problem is that the adapter has a spot for the 7-wire plug to fit, but there are no connections to it. This leads me to believe the four wires in the 7-wire plug are unnecessary. But I don't know. PURPLE/WHITE and GRAY are labeled "Instrument Panel Dimming Cell" in the GM manual, which is probably incompatible with modern stereos anyway. I can only guess through process of elimination the GREEN one is what the book calls DK GRN and that is labeled as "Entertainment and Comfort Data Line." What in Ernest P. Worrell's world is that? lol


Then that just leaves the BLACK wire which I can only guess is another ground wire of sorts for the others on this plug. And here is the adapter for reference (no pins/wires in the big one, lower left):



So yeah, this is where I'm at 😵 Any help you guys can provide is greatly appreciated as always.

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Alrighty! Got it figured! Appreciate the assist, padgett. Though unfortunately some of the wire colors on that chart aren't in my car and some in my car aren't in that chart lol


And I'll show my work a bit here, complete with a screenshot and a link to the shown spreadsheet showing the wiring connections using the Kenwood KDC-BT33 stereo unit and Scosche GM02B adapter. Hopefully it helps someone else out in the future. I tried to make it as easy to read as possible.



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  • 3 weeks later...

A side note for those looking for a good cd player with bluetooth for their Reatta. I'm sure this is a more common option these days, but as it turns out, the Kenwood KDC-BT33 stereo unit I'm using has the option to change the display to any color you want, so it can match the rest of the dash pretty well.IMG_20210331_225236209.jpg.44a5ab36aa46900a5869f235734784a3.jpg

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  • 2 weeks later...

 I have a similar Kenwood in my '90 Reatta, and I really like it. It doesn't look so terribly out of place and works great. Though I had it professionally installed, so I was no help to you for your installation! The unit as custom display colours and there is one which is nearly identical to the rest of the dash.


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