How to install aftermarket stereo using GM07B harness

[bigchieftaco90]

Okay guys, so my stock radio had a bulb going out so I thought that was enough to justify buying a new stereo. I actually just wanted to have Bluetooth, or at least an AUX input.
I found a cheaper stereo for $35 with Bluetooth AND decent reviews.
After looking at a few different wiring harnesses, I ended up getting the GM07B for $8.74.
I bought the Scosche stereo mounting bracket for $15.20.
I did ZERO research on aftermarket stereos in our bonnies. If I did, I would have found out how difficult it can be. I learned the hard way and figured I could write up a quick how to list for anyone else like me.

For SSEi models:
We have a factory amp. We have to make sure it turns on with the stereo or we will have no audio.
After digging, I found out that the A3 pin, 3rd pin from the bottom right, is the factory amp remote wire. We NEED to send 12v down this pin to power the amp.
Now lets look at the GM07B harness.


What do you know, no wire coming from pin A3. This is no big deal. All the brown wires are unused. Take a staple and straighten one end. On pin A4(brown wire) push the staple into that little square hole behind the pin(red arrow). Make sure its firmly pushed in and hold it. Pull the brown wire from the other end to pull the pin out of the connector.
Once it's out, push it back into slot A3. Now we have a remote wire for the factory amp.
**You could remove all the other brown wires using this method since we will not use them**

For all models:
Okay, so what's the big deal with this harness? Why do we need a write up? Well, most people don't know that the factory radio harness doesn't have an ignition cable. Even though the GM07B harness has a red cable, the factory side of it doesn't push the power to it. Trust me, I tried to hook it up and it didn't do anything.
There are a few options to get an ignition cable to the radio. The one I used since it was probably the easiest was to spice into the cigarette lighter cable. If you do this, make sure you have the fuses set so it will power off after a certain amount of time.

Under hood fuse box. Fuses are 22 and 23. They have 2 positions. One is for always on or only with retained accessory power.

*edit for pictures





In this position, they are powered by the RAC circuit. If you move them to the outer positions, they will be powered all the time.

Alright, now we have an ignition wire ran to the radio cubby. You will want to connect that wire to the red wire from the stereo side and red wire from the GM07B harness side. **SSEi: Also connect that A3 wire to power on the amp.
I hooked both yellow wires from the GM07B harness to the single stereo yellow wire. I also hooked all 3 ground wires to the single stereo ground wire. I'm not sure you actually have to use all 3.
I didn't use the orange wire from GM07B harness. I'm not even sure what it actually does, illumination? Maybe certain stereos use this.
All the speaker cables are self-explanatory.
The only other issue you will have is to get an antenna adapter. I have yet to do this because I'm not sure I need radio.
Here is what you want to use.

This is what the factory dock looks like.
|GND|RR-|RR+|LF-|LF+|open|open|open|open|open|open| GND | ILLU | ANT | +12v | +12v |
-----------------------------------------------------------------------------------------------------------------
|GND|RF+|RF-|LR+|LR-|open|open|open|open|open|open|open|open| AMP | data | data |


Conclusion: This was the most difficult install I have ever done. There wasn't any super clear posts out there describing what to do for this harness.
Things to note:
There is NOT much depth room to work with. I bought a very small stereo that didn't have a CD slot and I was still fighting the space.
You will lose door chimes.
You will lose power off when door opens.
You will lose On-Star
You will lose steering wheel controls.

If you want to retain all these things, you will not be buying the GM07B harness.

**I did this on a SSEi model. If someone notices this is way wrong for any of the other models let me know. I'll change this to SSEi only.

[nos4blood70]

This is awesome. Same harness I used for my non-amplified SLE.

Things to note:
99% of head units will require the dash plastic to be cut out behind the radio to deal with the aforementioned lack of space.

On-Star is dead and gone anyways.

Steering wheel controls can very easily be retained, just requires an extra little adapter(cost varies) and some extra wiring. The wire you want to tap into is in the steering column area and can be quite easily accessed by the removal of the hush panel directly underneath it. If I remember correctly, the wire is a blue color.

The orange wire is for illumination, it'll make your head unit's buttons come on/display dim when the headlights/fogs/parking lights come on. This is dependent on the head unit, however.

For SE/SLE models, if you don't want to use the cigarette lighter, you can tap into the IGN3 fuse in the rear fuseblock. The radio will power on with the ignition. The method in the thread might be easier for those without an aftermarket amp in their SE/SLE, but if you're already running RCA cables back there, it might be something different to consider.

Overall, very nice job Bigchief! This is extremely helpful, and IMO should be stickied.

[bigchieftaco90]

Thanks Carl! I appreciate the feedback and the VERY helpful followup of things to note.

I really like your way of hooking into the IGN. I will probably switch over to that when I install my subwoofers and amp. I'd just feel better about it knowing it's shutting off when I open the door
Sounds like an easy way to run a remote wire to the aftermarket amp too.

[jshow816]

Thanks for the write up. I'm thinking about purchasing this harness, but I have a question.. What is the point in hooking up the 12v accessory run to both the radio and the harness? Why exactly do you want to send 12v back to the dock & lock? Just asking out of pure curiosity.

[jshow816]

After looking again I see that the red wire on the scosche harness is in the place of the antenna turn on wire, so that is why you want to run the switched 12v to it. I bought this harness and will install it this weekend. Thanks again for making this, it should
make this job so much easier.

[jshow816]

Your instructions rocked! Thanks so much for posting this, made installing my stereo so much easier.

[bigchieftaco90]

No problem at all! I'm glad I could help