GMLAN and aftermarket radio Compatability issues

I have gotten mixed reports regarding removing the base stock GM radio and replaceing it with a aftermarket radio. Anywhere from the airbag NOT deploying in a crash to the car not passing the NYS emission inspection. No, I'm not making this up.

The radio is only the base model. with NO "Preference" controls. It can't even change the level of the 'chime'. With this class 2 data bus, where everything is tied into the LAN system, this has me worried with all these stories I have heard from local stores that sell radios.

Since this unit has no data functions other than being tied into the data bus for radio related issues (DTCs') and the 'chime' feature (which I could live without), if I don't go with one of those overpriced ($80-$100) adapter cable assemblies with the chime interface, is there any problem with this??

My car is a Chevy 05 Classic (fleet version of the Malibu). Call an installer, Circuit City, Best Buy. They can tell you if it is possible and what adapters are needed. CC & BB would be the last places I would ask. When some corporate type thinks his employees make too much $$ and fires them, I won't fund their gestopo like tactics.
I'm not spending $100 to hear chimes.

Anyone that is familar with GMs' data bus system regarding the factory radio? The radio is on the bus with the rest of the modules in the vehicle network. I don't see how installing an aftermarket radio can upset the other controllers, especially the BCM, as long as you don't connect anything aftermarket onto the data bus at the radio's connector. The only problem that you may run into with the other modules is that they will see that the radio is missing off of the bus, so they will set U codes. Its a class C code so you won't see any service lights. You can experiment by unplugging the factory radio and then driving the car around to see if you see anything unusual. The data bus wire is PIN A1 PPL (purple) on the radio's connector. Don't connect anything to that wire if you install an aftermarket radio. Quote:I don't see how installing an aftermarket radio can upset the other controllers
Neither do I, but according to some of these other 'horror' stories I heard, you would never know it. Frankly, AFAIC, it shouldn't be tied into the system at all! It's just a radio. Quote:Its a class C code so you won't see any service lights.
I have the Helm SM for the car and I saw no mention of any 'class' of codes anywhere. Do you have any source/site that has more on GMs' LAN system? Quote:You can experiment by unplugging the factory radio and then driving the car around to see if you see anything unusual.
I did. With my code reader (not a scanner), no code was shown. No U1128 code, which, according to the SM, should of been there (loss of communication with the radio).
I now question the code reader.

I wonder, since this radio doesn't even have the ability to change the 'chime' level (basic radio function) if it is even tied into the data bus. The chime control is actually inside the BCM (body control module). The BCM basically tells the radio over the bus to chime through the speakers. The BCM also control the radio's illumination when you have the headlamps on or you control the interior dimmer switch. You may not see a U code if you access the PCM. The PCM really doesn't need to talk to the radio. You may see a U code in the BCM but you need a scanner with the capabilities to communicate with the other modules in the vehicle.

Basically the codes that are set by a controller are classified according to priority or type. GMs highest priority codes are A codes. A codes turn the check engine light and are stored on the first time they fail. B codes will set the light and will be stored if an A code doesn't exist or if it fails the next run of a test or trip. C codes don't turn on the light and only get stored. data bus U codes are usually the C type.

I searched the internet for information on code classification and there really isn't any info. I learned this in training classes. Quote:You may see a U code in the BCM but you need a scanner with the capabilities to communicate with the other modules in the vehicle.
Code readers only communicate with the PCM? How about the $200-$600 OBDII scanners?
There are four LEDs' on the reader for the different types of error codes; Power Train, Body, Chassis & Uart. Wouldn't/isn't the "Uart" the "U1128" type code?? UART (Universal Asynchronous Receive and Transmit) is a protocol that was used in the earlier GMs. It's a bi-direction protocol that was used also in the (E&C) entertainment and comfort bus in mid 90's GMs that also used Class 2. Class 2 is the later protocol that is used for communication of all modules in today’s GMs. Class 2 rides on a 7Volt bus and is a lot faster than the UART's 5Volt bus architecture. As more modules are being added to vehicles, bandwidth in the bus needs to be expanded. CAN (Controller Area Network) is the newest protocol and is able to handle the increased communications.
Some scanners, such as the Global scanners are unable to communicate with any other modules on the network besides the PCM. They focus on OBDII information only. Scanner such as yours may be able to retrieve codes from other modules in the vehicle but may not be able to retrieve data stream information. I suspect that you may be able to communicate with the BCM using your scanner. What kind of scanner do you have? U code is the designator for any codes that refer to communications or bus operation, just as P codes refer to the powertrain. If I remember reading correctly, I thought I saw reference to a 'Class 1' data bus in this present car. This 'CAN' protocol, is this just GM, or all makes?
The "tester" is an Actron CP9035 code reader. I only have it because a friend owed me a favor and this was the return. I wouldn't of bought just a 'reader'. We are starting to see CAN in higher end cars, such as Mercedes and BMW. They are slowly trickling into domestics also. I don't know which ones but you may see some Cadillacs or Corvettes with it. There are different forms of CAN so I am not sure who is using what. I do know that CAN usually requires a controller or module that is strictly incharge of bus operation. Along the same lines as a Chipset in a home PC. I haven't heard of Class 1 before. Here is some Class 2 info for your Classic:

Data Link Communications Description and Operation
Class 2 Serial Data Link

The class 2 serial data link allows the following modules to communicate with each other:

* The body control module (BCM)
* The electronic brake control module (EBCM)
* The integrated radio chassis (IRC)
* The powertrain control module (PCM)
* The remote control door lock receiver (RCDLR)
* The inflatable restraint sensing and diagnostic module (SDM)

The class 2 serial data link also allows a scan tool to communicate with the above modules for diagnostic and testing purposes.
Data Link Connector (DLC)

The data link connector (DLC) allows a scan tool to communicate with the class 2 modules. The DLC is a standardized 16 cavity connector located below the instrument panel and close to the steering column. Connector design and location is dictated by an industry wide standard, and it is required to provide the following:

* Scan tool power battery positive voltage at terminal 16.
* Scan tool power ground at terminal 4.
* Class 2 serial data signal at terminal 2.
* Common signal ground at terminal 5.

Refer to Diagnostic Starting Point - Computer/Integrating Systems .
Diagnostic Trouble Codes (DTCs)

Each control module connected to the class 2 serial data circuit monitors serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. In addition, node alive messages are transmitted by each module on the class 2 serial data circuit about once every 2 seconds. If a module does not receive a node alive message when expected, a DTC will set. If a module detects that the class 2 serial data circuit is shorted, the setting of all other class 2 serial communication DTCs is inhibited, and DTC U1300, U1301, or U1305 will set.


Your actron is way outdated. It was really one of the first testers to come out for OBDII. That explains why you see UART. UART isn't used anymore in the newer vehicles. It is still good because you can read and clear OBDII codes from the PCM but that is about it. Your car also resets the oil life system threw the raido along with tire pressures and trans life. Just a few other things you might not have known.

I will post a reply on this when i get back from town on all your vehicle does via the radio. Quote:Your actron is way outdated. It was really one of the first testers to come out for OBDII.
What does/will thre newer models do that this doesn't? It was basically given to me. I would of bought a scanner. Quote:Your car also resets the oil life system threw the raido along with tire pressures and trans life.
That might be with the better models, but you can't even change the level of the chime with this one. This is a '05 Classic; the fleet version of the Mailbu. That is standard on all 05 malibu's. It still has to have an oil life reset and a trans life reset. You have to hold the Disp button for 45 seconds to 1 min and it will come up with the oil life reset.

Check your owners manual on how to reset the oil life on your vehicle. "Disp" as in 'display'? This radio doesn't have that.
I don't have the OM yet (on order from the dealer), but the factory Helm SM has no mention of this.
I will try it, but again, the radio doesn't have any control over even the chime level. The Classic doesn't have oil life monitor, transmission life, or tire pressure monitor. The only thing you can change through the radio is the chime level.

Here is the procedure:

In order to adjust the chime level, perform the following steps:

1. Turn the ignition ON.
2. Turn the radio OFF.
3. Press and hold the radio push-button 6 until either LOUD or NORMAL appears on the radio display. The chime sounds 3 times for each volume change.
4. To toggle the setting, press and hold the radio push-button 6 again.