Thread: Class 2 Data Bus

While it's true that class 2 databus uses the factory radio to program factory keyless entry, reset service lights and low tire pressure lights, but only on certain cars. I only know of some Impalas and Monte Carlos use this setup. Trucks, and J bodies only have chimers, XM and onstar to worry about. I have not done any newer GM cars where the removal of factory stereo caused the service light to come on. PAC do make a converter box for the class 2 data bus to allow you to replace the factory radio with aftermarket radio while keeping the chime and Onstar with Bose without relocating the factory radio. One down side is if your vehicle has XM, you will loose that feature. If all else fails relocate the factory radio to the trunk. Forget about mounting the radio under the seat or the glovebox. It doesnt fit.

It won't fit in my glove box? Class 2 data bus is on every GM that was made after the year 2000.
So, I might be ok to replace my stereo? It would be nice to not recieve those awful chimes when I don't get my seatbelt on by the time I have turned the engine on.

Its not on every 2000, The s-10 didn't get the new radio until 2002 and even then I bet they just made an adapter for it, why redesign the whole electrical system on a discontinued line. The main thing you will loose is the chime and the control over the car such as reset the oil change light or washer sweep. You can reset the oil change light in other ways and there are chime replacements available now.

alright... i have a 2000 cavalier z24 with the class 2 data system.

first off, i'd like to find the people at gm who came up with this idea and beat them with a pipe.

now down to business...

the radio in *my* class 2 data system is a sub-computer... basically it does its own thing on the side of the car's main computer system. so when i took mine out all i lost was the speed controlled volume, the radio power off delay, and the idiot chime. the reason the idoit chime is lost is that the radio plays the chime through the front left speaker. since the radio is run via the class 2 data stream, there is no ignition wire for turning the radio on.

so, there are a couple options... you can use a basic gm compatable wiring harness to hook up your new stereo. you will lose the all those features i listed above, but it is by far the cheapest.

the other option that you can do is what i did. several companies have available a specialized harness that lets you piggyback the new radio into your existing system. basically it is a T-harness that still lets the original radio recieve the class 2 data. some of them also come with a small speaker that you can hook up to the original radio to maintain the idiot chime. also, i put the original radio in the glove compartment, and it fit fine.

so, there are your options...NO lights will come on, your airbags WONT deploy, your car WONT stop running, or any of the other horror stories. the only way your airbags will go off is if you start screwing with the wiring while you are in the dash... dont cut or tap anything if you dont know what it is for

let us know what kind of car you have also...

~Mike

Thats what I was trying to say

I was very lucky my 2000 doesn't have the class 2 so I didn't have to do anything.

Its not necessarily a bad idea, I like being able to control the car. In my wife's Impala you can turn on or off the auto door locks, you can control how many swipes the wipers make when you run the washer. I think they should have added the ability to read the OBDII codes on the radio, that would make it great.

Oh thanks god that GM didn't use the class 2 or whatever radio in the Pontiac Vibe/Toyota Matrix. Otherwise, I am screw. Well I am screw now anyway because I have a Toyota car with a GM radio in there and no one is making an aux adapter for the radio.

Toyota did put a OBD1 reader in their cars back in the late 80s which called SuperComputer. Yes, the 87- 88 and early 89 Toyota Cressida, and Supra NA and Turbo had ODB1 reader installed part of the gauges where the clock is (On Supras). You can read error code, reset error code,service reminder, fuel level.

It sounds like you do have the class 2 bus then. The pre class 2 gm radios have aux adapters available. The aux plug on them is seperate from the mainn wiring plug so it won't matter what kind of car its plugged into. Does your radio have RDS on it somewhere?

I don't think the radio on my Matrix is GM class 2 because the radio doesn't interfere with the operation of the car like Check engine/service light or other problem stated in previous posts. The only problem with when replace that radio with aftermarket (some Matrix owners already did) is a crappy radio reception. There is some wire trick to turn on the antenna for better reception.

Originally Posted by MatrixPC

I don't think the radio on my Matrix is GM class 2 because the radio doesn't interfere with the operation of the car like Check engine/service light or other problem stated in previous posts. The only problem with when replace that radio with aftermarket (some Matrix owners already did) is a crappy radio reception. There is some wire trick to turn on the antenna for better reception.

Those were just rumors, you do't get a check engine or break the car.

Does your radio have RDS written on it somewhere?