Radio Class 2 Serial Data: Everything There Is To Know!

Like all other renowned vehicle brands, GM vehicles also have some unique features that are sometimes confusing to understand at first. Class 2 serial data is also a term like this which can be confusing. 

So, what is radio class 2 serial data?

Radio class 2 serial data is a communication protocol in GM vehicles where the radio works as a control panel. The Class 2 data is connected through a scan tool via a data link connector (DLC) to provide instruction to car instruments., for example, radio, amplifier, car door, and climate control. If the Class 2 serial data doesn’t work, you will face a problem controlling these mentioned devices. 

To know about this topic in detail, keep reading. 

What Is Radio Class 2 Serial Data?

radio serial code

Radio Class 2 (RCL2) is a communication protocol used by General Motors (GM) in their vehicles. 

A scan tool is connected to this class 2 serial data network through the data link connector (DLC). Through this connection, class 2 serial data allow various electronic components of a car to communicate with each other wirelessly. 

For example, the CD changer, radio, XM radio, amplifier, DVDs, automatic door controller, and climate control. 

When class 2 is connected to the scan tool, the microprocessor-controlled modules of the electronic devices of cars send information to the serial data network. 

As a result, this class 2 serial data can send information to the devices to provide instructions. For example, opening the door automatically or turning the radio On. 

So, if one of the devices connected to the class 2 serial data is faulty, it can detect them and show an error code on your car’s display. 

What Is Class 2 Serial Data Voltage?

The highest nominal voltage of Class 2 data is 7 volts when activated. And when the data is deactivated, the voltage is at ground potential, which means 0 volts. 

Class 2 serial data is transmitted at 10.4 Kbps (10,400 bits per second) at an average rate over a single wire. The operation speed of this module is not consistent and can be slower or faster. 

Also, while in the operating position, all the modules connected to the Class Two serial data keep sending information to it every 2 seconds. The information is about the state of health (SOH) to ensure the networks that the modules are working fine. 

What Happens If The Class 2 Data Is Not Working? 

If the Class 2 data is not working, you will face several issues in your vehicle. Devices that are connected through the class 2 data will stop working. For example, you will face the following problem. 

  • Radio, speakers, amplifiers, and other entertainment devices are not working.
  • Climate control is not working. 
  • The automatic door opening feature is not working. 

Usually when we face car radio issues, for example, when the jeep cherokee doesn’t work, we immediately jump onto the radio troubleshooting. 

But in this case, If you are facing these problems altogether, that means there is an issue with the class 2 data. In this case, you have to get the class 2 serial data repaired. Some repairs are not as easy as troubleshooting the Delphi radio.

However, you can still try performing some troubleshooting tips by following the video if you are familiar with these types of repair.

What To Consider While Removing Radio Class 2 From The Vehicle?

In some GM car models, the radio is assigned as the control panel for all the devices connected to the data network. And there is no additional 12v switch as the power is directly delivered to the radio plug. 

So, when you want to remove the radio of your car for any reason like the radio switching from aux to radio, you have to keep this in mind. When you remove the radio,  all the features still remain in the same setting. 

Changing the setting requires consulting the authorized dealer. Due to these reasons, while removing the radio, you have to source the Class Two power somewhere else. An accessory power source with a 10A to 30A fuse is recommended for this. 

So, the fuse panels including the windshield wiper fuse or the sunroof fuse can be good options. 

Also, if you want to replace the radio of your GM vehicle, try to replace it with a good-quality GM radio. The radio will last longer and provide better sound quality. 

Frequently Asked Questions (FAQs):

What Is Class 2 Serial Data Link Malfunction?

The Class 2 serial data malfunction is a problem with the Class 2 communication with the devices. In this condition,  one or more devices that are connected to the serial data are not sending a message or taking instructions properly. 

What Is The Code U1000 On A 2003 Chevy Silverado?

The letter U in the code U1000 on a 2003 Chevy Silverado means a communication problem. And the code, 1000 means, the CAN network is unable to catch up with one or the mode device module of the Chevy Silverado. 

What Is A Locked Gm Radio?

The locked GM radio is a condition where you can’t run the radio. When you enter too many wrong codes in the GM radio, the radio gets locked. It doesn’t mean the radio is broken or faulty. You just have to enter the right code to get the radio running. 


There goes all the discussion on radio class 2 serial data. I believe that would be enough to satisfy your curiosity on this topic and it’s not confusing anymore. 

Also, if you face any problem with this communication protocol, you should consult a professional rather than fixing yourself as many devices are connected. 

That’s all for now. Have a great day!


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