For years, I have been happy with the factory MP3 CD player swap I did on both my Monte and Grand Am (load a CD full of MP3s and go).
I have been getting an itch to do an AUX jack mod. Part of it is because my Grand Am is on it's 3rd radio (other two developed problems loading CDs, and back lights on the LCD have also been replaced now more then once). The other reason, cheap solutions to hold more music then a CD in a device without moving parts (like my cell phone).
I have no interest in aftermarket radios (I know there are some cool ones I can pair with these two cars that would be awesome, but there is also something to be said about having the factory look). There are after market companies that sell modded factory radios to include an aux jack for about $150+. I contacted one of these companies and they claim they inject the aux signal before the internal amp (so no matter what you have playing, plug into the aux jack, that music stops and the aux music begins). I tried looking for pin outs and info on how to do this (for obvious reasons, these companies did not want to share their secrets). Sadly, I could not find an answer.

So, on the Grand Am, with my dad's help, we did a mod many people with XM do. One difference. Most people cut into the XM wiring and inject the AUX jack that way (such as the link below):
XM Aux Jack
We cracked open the radio and made the change internal at the back side of the connector. I did the research, had the pin outs, dad did the soldering work. Mod works like a CHAMP! Hit XM, plug in an aux source and it cuts off the XM.

I mentioned this was a test for a Monte mod. Well it was in more than one way. My Monte does not have XM and for the past year I have been researching how to activate the XM option on the Monte so I can just abandon it to use for an aux jack. Sometime last year, I did a test with my Grand Am's XM receiver, I took it to the Monte and grabbed power/ground/data connections from the diagnostic port under the dash. Doing that, the Monte saw an XM receiver (gave me the XM option), but it was in theft lock.

I now have a junk yard XM Receiver and harness for the Monte (about $30 invested). I have been trying to figure out how to get power and data connections for the XM receiver without cutting any factory wires (but I'm willing to add pins to factory connectors). I believe I have an answer to all of those items and I'll share when I do this mod later on. The nice thing about GM, they may give the radios different face plates, but in the end, the wiring is usually the same (the shop book may not tell you all the available options for the various pins).

I found the XM connector that plugs into the radio has data pass thru pin! With the Grand Am apart, I disconnected the factory XM receiver. I wired in the data pin on my junk yard harness, grabbed power and ground from the diagnostic port under the dash (using an ODB-II splitter, it also allowed me to hook up a GM Tech II). The Grand Am radio successfully saw the junk yard XM receiver! Downside, the receiver was in theftlock mode. I wanted to confirm that even in theftlock, would the aux jack work (or does the radio disable the audio for XM when theftlock occurs). Good news, the radio could care less about the audio when the XM Receiver is in theftlock mode!
That was great news since the Tech II cannot re-program the XM receiver (I tried and it did nothing, did more reading and found others with the same claim). Looks like the receiver pairs itself to the first car it's tossed into. There is a company that can "reset" it, but since I have no interest in subscribing to XM or drilling the roof to add the XM antenna, I could car less, it can stay in theftlock mode.

So that is the Grand Am mod and the learning for a Monte mod! I also plan on adding a Grand Am Monsoon amp to my Monte (switch from a 6 channel sound system to an 8 channel) and swap the rear speakers with speakers similar to what I have in the back of the Grand Am.

For those who made it through my excitement, thanks for reading
Sorry I don't have more pics. I hope to take some more pics when doing this on the Monte.

 

Glad you got this done and it's working well. I've done this a few times to my cars in the past. There are a few guys who sell them predone on ebay and such but it's an easy enough mod - especially with that xm.

 

I am interested in those "pre-done" ones, as some of the vendors claim the aux jack will work no matter what audio source you are using, as it's tied to the pre-amp.... I wish I knew that "secret" but I cannot find the detailed specs of the chip driving my radio.

So, in the Grand Am with XM, did the easy mod. In the Monte, I am going to add an XM receiver to present the XM option and repeat the same mod after that. Nothing like goofing with factory stuff lol.

 

Over the weekend, I had to do something else on the Grand Am that required pulling the radio. I took the bottom cover off the radio and took a couple pics. The pins for the back connector were cut and then bent for easy access to do this mod. To ensure the pins stayed stationary, we covered them in heat glue.

I could not think of any where else on the car I thought an AUX jack would belong, hence why I like this being internal to the radio.

As I mentioned, to do this in the Monte, I need to add an XM receiver. I have been trying to decide where I want to store a receiver. I looked at old pics when I tore the dash out to change the evaporator core. I am wondering if there might be room behind the HVAC controls or maybe under the center console. Since I am not looking to actually get XM service, I'm not mounting an antenna anywhere, so that limits part of my issues/concerns.

 

Very clever Jason!
Nice to have an electronics Guru in the MCF family. As for your XM receiver location, that's gonna' be a challenge unless it's tiny. Maybe above the passenger knee bolster?

 

The soldiering work in my Grand AM radio I owe to my dad (I can handle a soldiering iron, but he has a few different one for different jobs and some better skill than I).

As for figuring out how to make my car activate the XM, that was all me.
Here are some pics from my XM tests last year. I pulled a XM receiver from a late model Cobalt at the junk yard. That uses a different system to talk to the car computers (I tested with my '04 Grand Am, seen in the attached pic).

But, I had enough of the Cobalt wiring harness, I re-ordered the XM receiver pins to match my Grand Am's receiver and parked the Monte and Grand Am close together, jumpered the XM receiver in through the diagnostic port on the Monte and WHAM! My Monte, which did not come with XM, now had the XM option on the radio (even though it says "XM Locked").

The receiver is rectangular in shape (I wish I knew a way to slim it up, since I am using it to hack the radio). I think there is enough room under the center console. But, I have to solve some issues. The Monte I have treated very unique with mods like that. I have had two rules and yet to violate them:
- No cutting any factory wires.
- No drilling/cutting any part of the body.

I hope to dig into this during the spring. I am certain, there is somewhere I can tuck this little module.

 

Jason I really like this thread! I don't listen to the radio much anymore because Iheart radio bought up most of the stations around home and they all play the same old songs I have been wanting an aux port so I could play music but I didn't want to disturb the original look. Cudos on the job and thanks for sharing the information. If my life settles down I might try this in the spring.

 

Feel free to add an aux port to my Monte when you get one in yours

 

Thanks guys. I have taken a small liking to hacking technology. The king aux jack mod is still tapping into the circuit board of the radio before the pre-amp and interrupting any audio.
But at $150 for that modded radio, no info on the Internet on how to make it happen, I can accomplish adding XM to get the radio to give me that option for a lot less.

Mike, you give me a curious thought. My radio is a MP3 radio (which GM did not offer in the Monte, but offered in the era of XM). I believe your Monte and your radio pre-dates GM offering XM. I wonder if it would acknowledge the XM receiver. I have a spare receiver and wiring I could bring to Carlisle this year. Takes about 5 minutes to test, no disassembly required (just going in at the diagnostic port).

 

Well the thing that throws me for a loop, is that my radio has a CD/AUX button next to the AM/FM. You are correct though, there is zero mention of any XM on the radio.