GM 21 pin radio, 7 more pins?
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=22588
Printed Date: July 18, 2025 at 6:05 AM
Topic: GM 21 pin radio, 7 more pins?
Posted By: donald7150
Subject: GM 21 pin radio, 7 more pins?
Date Posted: December 09, 2003 at 9:11 AM
I am looking for a diagram that shows what each pin does on my factory cassette deck in my pontiac, but all i can find is the pins for speakers, backlighting, ignition power etc, but there are 7 more pins on the deck that i cant figure out, does anyone out there know what they are for? 
Replies:
Posted By: Velocity Motors
Date Posted: December 09, 2003 at 9:58 AM
That would be the controls for the AUX tape or CD player ( Depending on what you have in the car at the time )
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Jeff
Velocity Custom Home Theater
Mobile Audio/Video Specialist
Morden, Manitoba CANADA
Posted By: donald7150
Date Posted: December 09, 2003 at 3:18 PM
yeah i kinda figured that but i would like to know what each pin does individually, like which pins are left and right signals, which supply power to the tape deck or cd player ect thanks
Posted By: sparkie
Date Posted: December 09, 2003 at 6:22 PM
What is the year and make of your Pontiac. The 7 connections you are referring to are not for the AUX in. They are for steering wheel control signals. (light green wire. The rest may not do anything depending on your radio. The AUX in is only on some Pontiac radios and is located in the back of the radio near the bottom center. If it's taped over you don't have an AUX in.
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sparky
Posted By: akimball442
Date Posted: December 11, 2003 at 2:24 AM
all completely digital GM radios made since 1990 do have line inputs on within those 7 pins. what vehicle did your radio come from? Not just pontiacs had it, but Buick, Olds, Cadillac... I have schematics for these, email me. on most of the radios the 7 pins are as follows (not in this order) Radio Mute (switches to the aux source) Steering wheel controls (2 wires) Left, Right and Ground for the Aux input, and another ground. A lot of them had an extra plug not included in the 21 pin harness. Sometimes that has the mute on it, it has outputs for illumination (a lot of vehicles in the late 80s and through the mid 90s that had digital climate control got their illumination dimming signal from the radio)
Posted By: donald7150
Date Posted: December 11, 2003 at 8:12 AM
the car is a '95 grand am, the radio has a tape deck built in, i know for sure are AUX in, my buddys '94 sunbird has the same plug, these 7 pins run to his CD player in the lower part of the dash, i want to see if i can hook a CD player up to it maybe have it sit in the center console
Posted By: sparkie
Date Posted: December 11, 2003 at 7:11 PM
Unless your radio has the separate plug in the center bottom back of the radio it won't have
aux in like your friends 94 Sunbird. These two radios are totally different. The factory option for AUX in wasn't added for a few years later than your car is. Sorry.
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sparky
Posted By: akimball442
Date Posted: December 11, 2003 at 7:47 PM
Yup, sorry bro, your car's factory radio is just an updated 80s model, dates back to 84. most of the 7 pins you have do nothing, two of them are for illumination for accessories on different model cars. Go on ebay, you can pick up a factory radio with the right connections for under a hundred bucks, or just grab the CD model with the 7 band EQ, its a decent radio if you dont want after market. peace
Posted By: donald7150
Date Posted: December 12, 2003 at 10:20 AM
alright guys this wasnt much help but thanks just the same
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