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Discussion Starter · #1 ·
I have a 04 GMC that I bought used, it has a XM radio that I just activated yesterday. Now I get all the channels on the display, but no volume (audio). It does not have Onstar. I stopped at dealer to ask if this was something that they had run into before. They found a bulletin on it and it said that the C2 connector (whatever that is) may be loose or unplugged. I was only going to get the XM service for 3 months because of the offer I got (3 months for the price of 1 for preowned GM vehicle) then more than likely terminate the service. Why pay for what I can get for free? (FM). LOL! They also said that it mayneed refreshed or reprogrammed or something? Does anyone know anything about this? Where is this C2 connector? Ther is no warranty on this truck (50,000mile), so I don't want to get a bunch of money wrapped up in something that I may not continue to use, so I'm going to try to fix it myself. Thanks

By the way, the 3 months for the price of one is called GM3FORONE for those of you who may have a preowned GM that would like to try it out, I told this to the XM operator and they said they would honor it, but a dealer must call them and verify some info.
 

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The C2 plug is the smaller of the two plugs (12 pin), that plugs into the back of your radio. You get XM selection on your Head Unit because that data is transmitted through the Data 2 bus. The right and left audio signals arrive to your radio through the C2 connector. I am impressed the dealer was able to give you an answer as to why you had no sound.

My truck had no XM or OnStar, so I had to "make" a C2 connector. See link...

http://dieselplace.com/forum/showthread.php?p=784227#post784227

Hope this helps!
 

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Discussion Starter · #3 ·
Thanks Dreamin'! Is that a pic of your truck? If it is, it looks just mine in the pic, mine is black with the cab lights and the XM radio that doesn't work.

I tore into the dash and found that there is no plug in that port, plus there also isn't any plug to plug into it. Why isn't there a plug? It was my understanding that all that I had to do was subsrcibe to the service and I would be in business? Now it seems as if I got sidewinded! :confused: Is there anything else that I'm missing? Censored



Also, why wasn't there any plugs in the trucks at the junk yard? Had they already been taken or they just never had them? Plus, were does these wires lead?
 

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Yes that's my truck. It's Carbon Metalic (color).

The junk yard trucks were crashed work trucks mostly... No XM or OnStar. One truck had it at one time, but someone beat me to it. I got an XM out of a 2005 Suburban and one of these days I will put it in and activate it.

Here are a couple of pictures that may help you... The factory XM unit (box), is located between your glove box and firewall mounted as you see in the pic. find the wire plugged into it and follow it to your radio. second pic is the actual pin diagram. Good luck! Let me know what you find.
 

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Discussion Starter · #5 ·
Dreamin',
are you saying that the wire that I need is already in the truck and I just have to track it down and find the end and plug it in? Or are you saying that I need to install this wiring?

I wouldn't think that I should have to do anything to a stock truck with factory installed XM radio?
 

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See #3 in the first pic? I don't know what you have... The XM box should be behind the glove compartment with harness (#3 in drawing) plugged into it. Do you see it on your truck?
 

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Discussion Starter · #7 ·
Yep

I can see the box and the wire harness plugged into it. It goes up and goes in with another set of wires, just as shown in the picture. But there isn't any plug, plugged into the back of the radio where you indicate the "12 prong" C2 connector (the one that you made) should be. From what I understand it is needed to run the XM audio? Yet I don't have any wiring for the smaller plug at the radio. Is this plug needed (small plug) in order for XM Audio (volume) to function?
I guess that it doesn't make any sense to me as to why this wiring isn't there now. It is a factory installed XM radio and the previous owner had a subscription for the service when he owned it. This is the first time that I have gotten a subscription to it since I've owned it and I have no volume on XM only. :confused:
Are you sure that we're on the same page here? Sounds to me as though your truck was manufactured without XM or Onstar, and if that is the case, I could see where you may have to add some wiring to get things to work. My truck has factory installed XM only and did work at one time.........at least the free GM trial was used with the first owner and the subscription was still in his name. I wonder if they changed from one year to another, maybe one needed the small plug and another didn't? Got me? Maybe my radio is junk? as far as XM goes? Any further help or ideas is appreciated. I haven't given up yet! ):h :ro)
 

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I'm pretty sure you need the 12 pin connector for XM audio. There are three audio wires that lead from the XM module to the radio. I'd look for that connector. If it came loose from the radio, it could be tucked behind the raido under the dash. Did you see the XM module? You can try tracing the wires from the module to the radio.
Dan


I can see the box and the wire harness plugged into it. It goes up and goes in with another set of wires, just as shown in the picture. But there isn't any plug, plugged into the back of the radio where you indicate the "12 prong" C2 connector (the one that you made) should be. From what I understand it is needed to run the XM audio? Yet I don't have any wiring for the smaller plug at the radio. Is this plug needed (small plug) in order for XM Audio (volume) to function?
I guess that it doesn't make any sense to me as to why this wiring isn't there now. It is a factory installed XM radio and the previous owner had a subscription for the service when he owned it. This is the first time that I have gotten a subscription to it since I've owned it and I have no volume on XM only. :confused:
Are you sure that we're on the same page here? Sounds to me as though your truck was manufactured without XM or Onstar, and if that is the case, I could see where you may have to add some wiring to get things to work. My truck has factory installed XM only and did work at one time.........at least the free GM trial was used with the first owner and the subscription was still in his name. I wonder if they changed from one year to another, maybe one needed the small plug and another didn't? Got me? Maybe my radio is junk? as far as XM goes? Any further help or ideas is appreciated. I haven't given up yet! ):h :ro)
 

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If you have the XM box with the plug in it, the 12 pin plug for the radio end has to be there somewhere. Unless someone at one time, stole the radio and cut it out, and the original owner, not wanting XM, didn't bother having it replaced???

Grab your gauge bezel trim, pull straight out, then remove the three srews holding the Head Unit in, pull the HU out and look good and hard. That smaller plug HAS to be there. It may have fallen down behind the radio somewhere you can't see.

If worse comes to worst, You will need to rerun (or have the dealer fix it), the audio wires to the back of the radio.

I personally would take it back to the dealer and have them fix it! Then have them or XM credit you back for time lost for it not being hooked up.

And YES, we are on the same page here... I just did mine and I'm VERY familiar with this... Just ask machomachodan... I bent his ear on this several times 2 months ago... Thanks Dan.
 

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Discussion Starter · #10 ·
Ok, thanks guys. I sure do appreciate the help.

I've dug and pulled and looked with mirrors back in there. It looks as if I'm going to have to take the top of the dashboard off in order to be able to see the wiring better. This is the original radio that the original owner had subscribed to originally. XM still had it in his name. Of course the wires from module mix in with another bunch of wires before they get to the radio, but I'm not able to track without removing top of dash. I removed the radio, heater controls trying to get back in there further to find that wire with no luck. Censored
The dealer that I bought it from is 200 miles away....so that's not an option for me. Plus it is out of any kind of warranty anyway.
I wonder why someone would disconnect it? Maybe they were paranoid that someone else may subsribe to it under their name and they would get billed for it? Or maybe the previous owner had the XM free trial service activated and it never did work? Who Knows!?
I will have to dig deeper, I will let you know

Thanks a bunch!
 

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Discussion Starter · #12 ·
I got it!!

I finally found that Censored wire/plug!!

I would have only had to remove the left hand passenger A/C vent had I known where it was! Of course I was on a mission and had already removed the vents/dash/post covers and tweeters before I found the wire. Although it was much easier to mess with the radio with dash off. Someone had unplugged that baby and pulled the plug end clear down towards the floor behind the center console towards the passenger side. Why would anyone unplug that thing? :rippedhan

Thanks a bunch everyone, especially :hail: Diesel Dreamin' for all the great help!:beerchug: and moral support!

I am tickled to death that is all that was wrong and it's working!:driver:

Thanks Again!
 

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Discussion Starter · #14 ·
I'm not familiar with the "Navigation" upgrade. Not sure what it is.
I'm sure that the wife is going to upgrade me :smashfrea if I don't quit buyin' stuff and upgradin' things as it is. One piece at a time. Lookin' to upgrade the exhaust right after the cognito lift kit. :drool: It's hard to talk the wife into putting more money into a $50,000 truck!

Thanks again for the advice!
 

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I'm not familiar with the "Navigation" upgrade. Not sure what it is.
I'm sure that the wife is going to upgrade me :smashfrea if I don't quit buyin' stuff and upgradin' things as it is. One piece at a time. Lookin' to upgrade the exhaust right after the cognito lift kit. :drool: It's hard to talk the wife into putting more money into a $50,000 truck!

Thanks again for the advice!
Just check out "My Garage", Plenty of upgrage ideas there... Some inexpensive, and some, well, ... nevermind. :eek::

You just have to convince her it's for "us". ;)

See picture for what the Navigation mod is... Note that I also added the 6 CD changer in the console also.
 

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