*** WARNING: This is going to be a LONG post. Before anyone says it, I know this is easier if I went for an aftermarket solution. I went down this road to do something different/unique. Even though I am currently at a point where I don’t see this project being finished for reasons I will explain, I wanted to share some information I learned that may help someone else or inspire other off the wall ideas.
Project Description:
Basically, I am used to the 8 channel Monsoon sound system in my daily driver, a 2004 Grand Am. I feel it sounds better than the factory 6 channel system in the Monte Carlo. I wanted to bring a better factory sound system from one car into another car it was never designed for.
One other item to notate. I do NOT like cutting wiring that is original in the car. That being said, I do everything I can to make plug and play harnesses or in some cases, add new pins to existing connectors. But never cutting the original wiring!! Also allows for an easy back out plan if needed.

Interesting Info about Monte Carlo Premium Sound Package (RPO code UQ3):
In all 2000-2005 (I don’t know about 2006-2007) Monte Carlos, this is a 12 speaker (6 pairs) sound system. But how it was designed differs:
In 2000-2001 – It appears that GM output 4 channels from the amp. The front has a woofer and tweet, but those speakers are supplied signal from the same channel. The rear has 6x9’s controlled by one channel.
In 2002-2005 – GM is using 6 channels from the amp. The front woofer and tweeter are independent from each other (completely different signal wires) and then you have the rear 6x9 channel.
The amps between the two year ranges are different and not interchangeable. All of this is validated by trips to the junk yard and research in the GM shop manual for the various years.

The first pic below is of a 2000-2001 Monte with the UQ3 front speakers. Take note, it's a 2-pin connector and wires going to the tweeter are jumped off the woofer (direct from the connection from the amp).
Next are pictures of a 2004 Monte speaker with the UQ3 option. Ignore the speakers missing (I am up to another project and did not want to buy the speakers, just the mounting plate and wiring). Notice the 4-pin connector and how the tweeter and woofer have their own signal wires.







Interesting info about the Grand Am Monsoon Sound Package (RPO code U85):
The rear 6x9s are multi-channel speakers. Basically imagine when you go to the store and buy some aftermarket 2 or 3 way 6x9 speakers, in that example, you bring one set of signal wires to them. Imagine same idea, but the woofer part has one set of signal wires and the additional part has its own. That is Grand Am Monsoon speaker.
Side note: Some Buick Regals had the Monsoon package and the rear speakers were two different pairs of speakers (not the way the Grand Am was done). But for this, I am working off Grand Am.
The pic below is of a Monsoon rear speaker set up from a Regal.



Monsoon 6x9 Common Problem:
Sadly, these speakers have a fault that the rubber surround around the cone dry rots, speaker fails and then sounds bad. Some people fix it by re-wiring the speaker output so the rear channel goes directly to the speaker and bypasses the Monsoon Amp. Others install an aftermarket speaker and only use on set of the signal wires from the amp (taking an 8 channel system to 6 essentially). And others have done what I did. Grand some multi-channel aftermarket speakers, re-wire them so they will now accept two different channels instead of just one. In the Grand Am I used an older pair of Rockford PUNCH 6x9’s.



And now the Monte

Monte Rear Speakers:
Last year I upgraded my rear Monte speakers with newer Rockford PUNCH 6x9’s. I wired them like I did the ones I put in the Grand Am (using a clip of a connector from the junk yard). I also made an adapter so I could still use them with the Monte’s factory amp until I made certain I wanted to go full Monsoon or not.
The one pic of the black sticker is the Rockford in my Grand Am. The other ones are currently in the Monte.






Missing Radio Connection for the Monsoon Amp:
The Monte has all the inputs/outputs the Monsoon amp requires except a couple. Such as the rear 6x9’s require a 4 pin connector for each speaker (each pair of pins is for a single channel). Plan there was to abandon the Monte 2-pin connectors and since the amp is in the trunk, simply run the correct connectors. That is an easy one.
The hard one is the Monsoon Amp requires a connection labeled “Gain Control Signal”. When looking at the 2000-2001 Monte, the radios had that feature but it was labeled “Amplifier Signal” (difference in authors of the shop books). And this connection was ran by the factory to the amp (but not in my 2004 and I suspect not the 2002-2005).
In my 2004 Monte, I found the factory wiring in the car has this wire partially ran. It goes from the radio to the passenger side fuse block and dead ends there. I found the fuse block does pass the connection. It requires adding a pin/wire to the harness facing the outside of the car to pin B6 (without the battery connected, I used a volt meter to validate connectivity between the wire I added and the harness for the radio). I then ran the wire to the back of the Monte along a factory wiring harness.

The purple wire seen in the pic below is the one I added "Gain Control Signal".



Junk Yard Monsoon Parts:
I grabbed a Monsoon amp from the junk yard. I also grabbed a huge piece of the Grand Am/Monsoon wiring harness. I did NOT cut the rear speaker connections from the harness (those are intact until I decided to shorten them later in the project). I took a generous cut of the rest. I also grabbed an extra amp bracket for the Monte.
Once home, I modded the casing of the Monsoon amp with studs to bolt onto the Monte bracket. I also took the clip of the wiring harness to make a “plug and play” test harness.







Testing the Monsoon Amp in the Monte:
Pretty straight forward. I unplugged the old amp and pulled it out of the trunk, put the Monsoon amp up there and plugged in the harness I made. Sure all the cable lengths are long, but it’s a test harness. The “Gain Control Signal”, I just temp wired together. I then gave it a go (I believe I drove it around for about a week). This came with some good and bad.
The good, it works. Made an 8 channel audio system like the Grand Am has.
The bad, it did not sound right. It took me a while to figure it out. I thought of ideas such as, the Monte front woofers are 6” round and the Grand Am uses 4x6 speakers, or the Rockfords I am using in the Grand Am vs. the Monte are multiple years apart, could be a generation change in the product. It took a while, but I believe I eventually clued in on the problem. The Grand Am has Bass/Treble/Mid sound adjustments. The Monte only offers Bass/Treble. If I take the Grand Am and dial the Mid adjustment to the center, there it is!!! The Grand Am and the Monte, for the most part sound identical!! I don’t have a way to adjust the Mid-range setting in the Monte!!!





Options to get Mid-Range Adjustments:
I have looked into many options to try and find a way around my issue and nothing seems to work. Keep in mind my factory radio is NOT the original radio that came with the Monte (I am actually using a radio that was never offered for the Monte, it’s the MP3 radio from a 2004 Cavalier). Despite that, the factory Monte radio did not have the Mid range adjustment.
But I will share what I have done:
1. – Using a GM Tech II, on the Monte Carlo, attempt to re-program the radio as a Pontiac Grand Am with the Monsoon/U85 option. Doesn’t work. It programs it, but does not add the Mid option (I am guessing that logic is not built into the Chevy radio).
2. – Take Grand Am Monsoon radio and program it in the Monte Carlo with the Tech II. It programs, provides the midrange option, if I recall chimes work. But two problems. First it looks out of place (none black front, red back light and gray buttons). Second it will not give me the additional options for programming key fobs, resetting the oil and tire pressure systems. I know there are alternative methods to those systems, but if I am going to use those alternatives, I might as well aftermarket this entire thing and be done with it all. Also, the display back light on the Pontiac radios dies. I’ve had a family member replace the back light bulbs on my Grand Am radio twice!
3. – Get a MP3 factory radio from a truck that offers the mid-range adjustment. So, the radios share the same connections, it will plug in, it appears to work if the radio is not in theft mode. Downside, the GM Tech II can’t get the two to play together. The GM Tech II can talk to the Monte and can talk to the radio, but no matter how I attempt to program the radio, the Tech II claims successful (I think it just means it sent the command and the radio received it), but the radio never gets out of theft mode. I am wondering if the truck radios entered the next generation in GM’s CANBUS network. Even if it worked, I suspect features will be missing that I want to retain.

Why This Project Won’t Be Finished:
If you read all of this, then you already know. The bottom line comes down to as much as I like the sound of the Monsoon system in the Grand Am, if I cannot get my radio to present a MID adjustment with Bass and Treble, I am not happy with the sound as I need to adjust the mid range setting.
So that is it folks, this is where this journey comes to an end. Stopped dead because I cannot tweak the mid range setting.

Side Note: If I carried this project to completion, because the odds of ever going back to the Monte original amp would be slim to none, I was planning to re-pin the Monsoon connector. Meaning, using a straight pin/pick/paperclip, safely remove the pins from the Monte amp connectors (and the Monsoon connector) and click the Monte factory wires into the appropriate position on the Monsoon connector (so no harness is required and this would appear factory).