GM Stereo integration harness.

[maritoze 10+ year member]

Are these things absolutely necessary? Is there more to them than just chime retention?

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[daboyfrumdabx 10+ year member]

Not absolutely necessary in most cases. What kind of car is it? Usually you can get away with a cheaper harness and you'll lose the chimes and 10 minute playback (when you turn off the car and the radio stays on until you open the door). Depends on how much work you'll need though. You'll likely need to run your own switched power wire and possible an amp turn on if your car has a stock amp.

 

[daboyfrumdabx 10+ year member]

Also, if it's a Best Buy or shop price of the retention harness that bugs you, keep in mind you can likely find it on ebay for less than half of what they're asking.

 

[arctictwist 10+ year member]

I used the PAC unit for my silverado, its a mess of wires. But i like that it retained factory wiring harnesses and made everything relatively easy except for fitment. Such a mess. I dont understand why the square unit needs wires coming out every side. It could be designed better to make things neater but it got the job done. It retains xm if you want, i chose to get the xm tuner that goes with my head unit for usability. IF you use the pac it transfers xm control to the DIC. I didnt like the sound of that at all. Definitely shop online, much cheaper.

 

[keep_hope_alive Premium Member]

Thanks to 300HP on SoundDomain for providing this info:

Hopefully this will clear things up for anyone who has wondered about replacing the head unit in a newer GM with the class II data bus system.

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What is Class 2 databus ?

Affects of removing Class 2 from your vehicle

Factory Deck Removal Process

ABS Concerns

Affected Vehicle List

What About OnStar ?

New Peripheral Interfaces Available

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What is Class 2 databus ?

The Class 2 system is a Serial Data Link used by GM in its vehicles, and is based on the SAE J1850 protocol, which is widely used in the U.S. It is through this data link that the body control module (or BCM) receives information and commands that are essential in determining its mode of operation.The BCM is connected, through Class 2 wiring, to the instrument panel cluster (IPC), the powertrain control module (PCM), the data link connector (DLC) and the radio.

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 II. Since these new modules are part of the audio system and security system, you are now hearing more about Class II.

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.

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Affects of removing Class 2 radio from your vehicle

Vehicle Customization Menu Options:

( Most Cavaliers, Sunfires and other base models do not offer most, if any of these features.

Check the vehicle owner’s manual to see available features. )

Displays current settings

Oil life monitor reset

Tire inflation monitor reset

Delayed headlamp illumination

Automatic door lock and unlock

Remote visual/audible verification of remote lock/unlock

Enable/Disable content theft

Enable/Disable trunk lock shock sensor

Short or long horn with remote lock/unlock

Key fob transmitter programming

The radio is used as a control panel to communicate with the vehicles computer for the customization of certain “convenience features”. All features work and remain at current settings with the factory radio removed, but can only be customized and/or reset by an authorized service center. More important than the above features and chime, there is no switched 12vlt. power supplied in the radios plug, so it will need to be sourced somewhere else such as the factory fuse panel. A 10A to 30A fused accessory power source is recommended. Depending on the vehicle there are several choices in the factory fuse panel, such as the sunroof or windshield wipers.

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Factory Deck Removal Process

Pontiac Sunfire OEM Removal Process & relocation harness installation

Each vehicle will have a different radio removal process & each vehicle has a special harness for it's relocation or Onstar peripheral interface. As with most of the 2002 - 2003 vehicles, the OEM radio has the vehicles VIN number encoded into it's memory and if this VIN number does not match the vehicles BCM, the radio becomes inoperative.

You can remove the factory deck, but you cannot sell it to someone else and put it in their vehicle. There may be a way to re-program the VIN of the radio to a different vehicle's VIN, but this will be something an authorized GM dealer will be able to tell you.

We will be updating the section of OEM radio removal consistently so please come back regularly. If you wish for a specific vehicle to be highlighted, please email technical support and we will see what we can do for you.

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ABS Concerns

GM’s service document numbers 537803, 558212, and 558208 give detailed instructions on removal of the radio. Document 537803 is the basic removal and installation referring to 558212 for the trim plate bezel replacement, and to 558208 for disabling the SIR system. Not suggesting things shouldn’t be done to procedure, but I‘ve spoken with a handful of GM service techs and not one follow these procedures when removing a radio.

Disabling the SIR system

1. Turn OFF the ignition.

2. Remove the SIR Fuse from the fuse block.

Important: With the SIR Fuse removed and the ignition ON, the AIR BAG warning lamp illuminates. This is normal operation, and does not indicate an SIR system malfunction.

3. Remove the IP insulator panel

4. Remove the connector position assurance (CPA) from the driver yellow 2-way connector located at the base of the steering column. (CPA is the little blue or green pin that prevents the 2-way connector from vibrating apart)

5. Disconnect the driver yellow 2-way connector.

6. Remove the connector position assurance (CPA) from the passenger yellow 2-way connector located at the base of the steering column.

7. Disconnect the passenger yellow 2-way connector.

Enabling the SIR system

1. Connect the passenger yellow 2-way connector located near the base of the steering column.

2. Install the connector position assurance (CPA) to the passenger yellow 2-way connector.

3. Connect the driver yellow 2-way connector located at the base of the steering column.

4. Install the connector position assurance (CPA) to the driver yellow 2-way connector.

5. Install the IP insulator panel.

6. Install the SIR fuse in the fuse block.

7. Staying well away from both air bags, turn ON the ignition.

7.1. The AIR BAG warning lamp will flash seven times.

7.2. The AIR BAG warning lamp will then turn OFF.

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Affected Vehicle List

Aztec 2001-2003

Cavalier 2000-2003

Envoy 2002-2003

Grand Am 2001-2003

Impala 2000-2003

Malibu 2001-2003

Montana Van 2000-2003

Monte Carlo 2000-2003

Sunfire 2000-2003

Trailblazer 2002-2003

Venture Van 2000-2003

There is another group of vehicles using class 2 data. The Oldsmobile Aurora, Buick LeSabre and Pontiac Bonneville use a flatwire or ribbon cable type connection @ the radio. This is also referred to as GM’s “dock and lock” setup. Until a harness, in my opinion a complete rewire is easiest for aftermarket head installation. Cadillac and some Corvette’s also have several models using class2 but further info is not yet available.

There are more vehicles with the Databus 2 system that is not on the above list and if you know of one please email us the year, make & model.

What About OnStar ?

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When you remove a radio from a vehicle with OnStar ( application list below ) you loose the speaker capabilities of the OnStar system. Ventura & Metra have teamed up to make a peripheral interface for the OnStar system if you want to remove the factory radio and retain the functions of the OnStar.

OBDII GM Class 2 Data Bus Peripheral

New Peripheral Interfaces Available

As of April 2003 there will be two new peripheral interfaces available that will allow the removal of the GM Class 2 data bus radio and retain the OnStar system after removing the factory radio.

Please contact us for these peripheral interfaces or if you have updated information on any of the GM systems.

 

[keep_hope_alive Premium Member]

Sure it's a bit old. But it gives more insight.

 

[keep_hope_alive Premium Member]

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 II 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 II, 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 configuration and 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 direct.