PAC AAI-GM24 Auxilary Input Problem - Need help!

[Zing]

I installed the PAC AAI-GM24, everything went smoothly, radio works fine, plugged in my MP3 player and it doesn't play at all. I followed the intstructions and tried pressing "CD/Aux" once, then twice, then with the MP3 player on, then off...NOTHING!!!

I have the '04 radio with 6 CD changer, which is supposed to work.

And I thought the challenge was getting at the back of the radio (thanks Happy Jack and others for their posts on this, takes patience but a breeze).

[Zing]

I installed the PAC AAI-GM24, everything went smoothly, radio works fine, plugged in my MP3 player and it doesn't play at all. I followed the intstructions and tried pressing "CD/Aux" once, then twice, then with the MP3 player on, then off...NOTHING!!!

I have the '04 radio with 6 CD changer, which is supposed to work.

And I thought the challenge was getting at the back of the radio (thanks Happy Jack and others for their posts on this, takes patience but a breeze).

[Zing]

I installed the PAC AAI-GM24, everything went smoothly, radio works fine, plugged in my MP3 player and it doesn't play at all. I followed the intstructions and tried pressing "CD/Aux" once, then twice, then with the MP3 player on, then off...NOTHING!!!

I have the '04 radio with 6 CD changer, which is supposed to work.

And I thought the challenge was getting at the back of the radio (thanks Happy Jack and others for their posts on this, takes patience but a breeze).

[Klaus]

Which version do you have? There appears to be two versions of the adapter.

One with 12 and 24 pin connectors (older version):

http://www.pac-audio.com/instructions/aai-gm24.pdf

Newer version, 12 pin connectors only:

http://www.pac-audio.com/instruction...4-04.07.04.pdf

If you have the newer version, did you connect the yellow and black wires? Yellow needs constant 12v, and black is ground.

You will probably not use the Red and Orange wires, so they can be taped up and tied out of the way.

[Zing]

I have the new version and crap, no, I just taped up the extra wires. I read "if an auxilary source requires a 12 volt accessory" to mean if my MP3 player needed a 12 volt power input, then...

So do you and tap the actual wires? Like cut the wire coating and solder into it? Or do you somehow tap that plug they show in the instructions?

[Klaus]

The instructions are pitiful. It looks like PAC decided to save money on the plugs by making you figure out how to connect the wires to the 24 pin connector, as opposed to providing a plug-in solution like they did with the first version. Shame, shame...

Anyway, I had to solder wires to the 24 pin connector when I installed my 6 CD Changer. First, you need to remove the connector pin locks from the connector. I then used a mini screwdriver to extract the pins, one at the time, from the connector, then solder the wire to the "crimped" area of the existing pin. You have to be careful here, as too much heat will melt the existing wire, and too much solder will keep the pin from fitting/locking back into the connector. Then push the pin back into the connector until it locks. You might need to bend the locking tang of the pin back into shape before it will lock. Finally, re-assemble the connector pin locks.

Quick connects *might* work instead of soldering, but space behind the stereo when mounted might be an issue. I suppose you could unwrap some of the tape from the wiring to the 24 pin connector, to clamp the quick connector on the factory wire further away from the radio connector.

BTW – Be sure to disconnect the battery before doing any of this.

Good luck - Let us know how it goes...

[Zing]

Thanks Klaus, very helpful. I'll let you know how it works out.

[Zing]

General radio question. Right now when I select "CD/Aux" nothing happens. Stays on FM. Or when I cycle through the bands using the "Band" button, no auxilary channel is displayed. Does this change when I hook up the PAC auxilary?

[Klaus]

Zing,

You know what? Now that I look at the wiring and instructions, I wonder how this thing is going to work.

All the radio accessories I have seen need a connection to the GM Class 2 Data Bus to "announce" itself as an available device, so that the head unit will show it as an option. The GM 6 CD Changer, and the GM XM Radio Tuner does this.

The problem is, the "new" style PAC unit you have does NOT have a connection to the Class 2 Data Bus! The Class 2 Data Bus circuit is in the 24 pin connector (pin A1).

I think someone may have goofed on the re-design of this thing! I'll be real surprised if it works!

[Klaus]

Zing,

Are there only 4 "loose" wires coming out of the adapter, as the instructions show?

[Zing]

Yes, there are 4 loose: red, black, yellow and orange. Do you think the red (12V accessory output 500mA) should be connected to "announce" itself? Or is that to power an accessory?

Interestingly, and I don't know if this means anything, the instructions show 6 wires come from the 12-pin connector into the auxilary unit, and mine only has 4???

[Klaus]

4 wires are all that are needed to be "added" to the 12 pin connector. Those are L+, R+, and common audio, and a "drain" wire.

The real problem I see is that you are missing a connection to the Class 2 Data Bus. I wouldn't attempt to connect one of the other wires to it! You could really do some major damage to your truck's electronics! BTW, the airbags are tied into the Class 2 Data Bus! You did disconnect the battery, right?

My suggestion would be to temporarily connect the adapter up to test it. Just connect the yellow wire to battery + somewhere, and the black to ground. No need to solder, just run a jumper wire from some other 12v source (maybe the 12v power outlet connector). Then power up your radio to see what happens. Don't hook the red or orange wires to anything without first calling PAC!

I suspect you will be sending this unit back.

[Zing]

Should the yellow wire be connected to "constant" power or only when the ignition switch is on. I don't feel comfortable with true constant power, nor do I see why that would be needed.

Thanks for you advice Klaus. My plan is to ask PAC a few of these questions and try again next Saturday.

[Klaus]

For testing it would not matter. For permanent connection, I'd connect it to the 24 pin connector, pin B1, as shown in their instructions.

Maybe you can swap out this unit for the original version. Then it would be plug and play!

[TouchdownTN]

I almost ordered this unit on Friday and now I'm glad I didn't. If it isn't plug and play I don't want it. After my experience with the Soundgate adapter I only want something very simple to install. Please post to the board what you find out from PAC!

[Zing]

Here's the reply I got today from PAC technical support. I'll try again this weekend when I have time and let you know how it goes.

The yellow wire needs to be connected to a 12volt source on the factory 24 pin connector, and the black wire needs to be connected to ground. I sent the instructions and a pin diagram for you to look over. The radio will automatically recognize the unit, all you need to do is push the aux/cd button to access the auxiliaries.


Thank you,
Joe Riggs
Tech Support

PAC
1502 S. Santa Fe St.
Santa Ana, CA 92705
www.pac-audio.com
714-835-3022
800-854-3133

[Klaus]

Update on the Avalanche Forum:

http://www.chevyavalanchefanclub.com/cafcna/index.php?board=160;action=display;threadid=24617; start=new

[Zing]

Hey Klaus, stupid question...what exactly is a GM Class 2 Data Bus?

[Klaus]

Demystifying Class 2
By Karl Yama****a
March 4, 2003

A lot of installers, dealers and customers have asked many questions on Class 2 so I wrote this small article to clear some things up.

Introduction

What is Class 2 in GM vehicles that everyone is hearing about lately?
Class 2 or Class B is really a in-vehicle network SAE J1850 protocol that GM has been using for many years. It just a new data protocol that a majority of vehicle computer modules uses, which share the same single data wire through out the vehicle.
Recently GM has now included the driver’s door module, passenger’s door module, rear seat audio controller, vehicle communication interface module or OnStar®, steering wheel audio controls, rear seat entertainment (RSE), CD changer, radio, DVD/Video, amplifier and XM radio as part of Class 2. Since these new modules are part of the audio system and security system, you are now hearing more about Class 2.

Connected to this same data wire is the Body Control Module (BCM), Powertrain Control Module (PCM), Transfer Case Shift Control Module, Heater & A/C controls (HVAC), Inflatable Restraint Sensing and Diagnostic Module, Theft Deterrent Control Module, Memory Seat Module, Drivers Information Center (DIC), Key/Lights/Seatbelt Chimes (most vehicles), Instrument Panel Cluster (IPC), Suspension Control Module, Electronic Brake Control Module (EBCM) and other modules.

Frequently asked questions

Do all these modules communicate at the same time?
Yes they do. Each module on the bus has its own ID number and is sent out every two seconds as a state of health message (SOH) to let other modules know that it is present. Every module sends information to other modules when needed. When the ignition is first turned on, there could be as many as 100 or more messages sent on the data bus from various modules within 1 or 2 seconds.

How can all the modules communicate at the same time and not interfere with one another?
Well first, all the modules have a Data Link Controller (DLC) chip with and internal or external transceiver physically connected to the data bus. And second, each module is assigned a different level of priority. The DLC is the key to the Class 2 bus. It is designed to send and receive data depending on priority. When each modules sends information over the data bus, they also check to see if there is other data activity on the bus. If that module sees other data while it is sending data and it has low priority, it will stop sending and try again when the data bus is inactive.

What happens if one module goes bad or power is disconnected from it? Will it load down the data bus and disable crucial control modules like the PCM or BCM?
Again, the DLC chip or transceiver is the key. It is designed so that even if power is interrupted or it damaged, it will not affect the data bus. So lets say if the radio power was disconnected but it was still connected to the data bus, it will not interfere with any other control module’s communication on the data bus.

Does your product use the DLC chip?
Yes they do. We incorporate it in our products to insure your safety when you drive your vehicle. You may pay alot more for our products for Class 2, but is your life or family worth saving a few dollars?

Is it true that the factory radio is related to the airbags?
No. The factory has nothing to do with the airbags or any other modules. The airbags are controlled by the Inflatable Restraint Sensing and Diagnostic Module.

Why are the factory radios being relocated when installing an aftermarket stereo?
Some vehicles have chimes built into the radio. When ever the key is left in the key cylinder or parking lights left on, the radio sends audio chimes to the speakers or to amplifier (if equipped). If the radio is removed, there is no way for chimes to be heard. Seat belts are part of the chimes also, and if not retained could result in the driver not using the seatbelt. The retailer installing an aftermarket stereo could be liable for injuries if the driver was to get into an accident and not wearing a seatbelt.

Can using a test light on the data bus cause damage to modules on the bus?
No, the DLC chip or transceiver is short circuit protected to ground and to voltage spikes up to 40 volts. The worst thing that will happen is that modules will not be able to send SOH messages and data information. Basically the engine won't run unless the BCM, PCM and other modules can communicate to each other.

I've heard that one vehicle would not start if the factory radio was removed. I thought the radio has nothing to do with any engine control modules?
Currently we have not run into a vehicle that has this problem. We wonder if the installer had a wiring issue that may have disabled the data bus?

I tried to put a LOC at the headunit but the volume of the aftermarket amplifier does not vary with the radio volume. Why?
Some vehicles have fixed audio signal outputs going to the factory BOSE amplifier. The BOSE amp only accepts 2 channels of audio from the front outputs of the factory radio. The rear outputs of the factory radio go to the RSE. When you adjust the volume/fade/balance or even EQ settings, the factory radio sends data to the factory amplifier. The factory amplifier actually does all the fading/balancing and adjusts EQ settings directly.


All other information on the vehicles are confidential and cannot be disclosed.
If you would like more technicle information on Class 2, you may do a search on 'J1850 and/or Data Link Controller' on the web.





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Pacific Accessory Corporation
1502 S. Santa Fe St. • Santa Ana, CA 92705 • USA
Voice: (714)835-3022 • Fax: (714)835-3233
Copyright © 2002-2003 PAC • Designed by Tatung

http://www.pac-audio.com/mainpage/class2.htm

[Zing]

Thanks Klaus! That is actually very interesting.