Will steering wheel controls still work?

Dedicated car stereos are made for specific year, make and model of vehicles. Generally this type of car stereos have specific requirements for installation, such as the plug of your factory car radio, the size of the car dashboard, etc. Sellers often list the installation requirements in the product page. If the dedicated car stereo is suitable for your car, then steering wheel controls (hereinafter referred to as SWC) can be retained after installing, such as volume up/down, previous/next track, answer/hang up calls, home button, return button, mute button, etc.

How to set up the steering wheel controls of dedicated car stereos?

The SWC function of an dedicated car stereo is automatically identified through CAN bus. After you install the car stereo, SWC will be available once the CAN bus is connected. No setup required.
Take Eonon R63 Mazda 3 car stereo as an example, CAN bus is included inside the package. As long as your car is 2010-2013 Mazda 3, and the car dashboard is right for installation (as shown in picture 2). You can install the car stereo directly and SWC will be retained.

Click here for more Eonon dedicated car stereos >
https://www.eonon.com/Newest-android-car-stereos.aspx

Note: Not all steering wheel controls are supported by aftermarket car stereos. For example, some Mazda car stereos do not support phone control button and voice recognition.

Different from dedicated car stereos, universal car stereos are not only designed for some specific car brands. It can be installed on various cars, such as Jeep, Audi, Ford, etc. Generally, installation kit and harness are needed when you install a universal car stereo.

How to set up the steering wheel controls of universal car stereos?

Before we go into the details, we need to learn about what car radio signal is.
There are two main types of signals: Analog signal and Digital signal. Analog signal is a continuous signal in which one time-varying quantity represents another time-based variable. A digital signal is a signal that is used to represent data as a sequence of separate values at any point in time. Analog signal and digital signal can be transformed from one to each other.
The signal of some car’s SWC is transmitted through analog signal while SWC of some cars is decoded by CAN bus.
If the signal of your car’s SWC is analog, then SWC can be retained after installing an aftermarket car stereo. It will be available after steering wheel control wires are connected.

How to connect steering wheel control wires?

Just connect the SWC wires of the car stereo to your car’s SWC wires correspondingly. After connecting, you need to refer to the user manual to set up SWC.
Take Eonon R03 universal car stereo as an example, the setup steps are as follows:

Click here for more Eonon universal car stereos >
https://www.eonon.com/Android-Car-GPS/Double-Din-GPS-Navigation.html

What if the signal of my car’s SWC is digital?

If the signal of your car’s SWC is decoded by CAN bus digital signal, you need to purchase a SWC adapter cable to transfer digital signal to analog signal.
How to connect the adapter cable? Just connect one end of the adapter cable to your car’s SWC interface, and the other end of the adapter cable to car stereo’s SWC wire.

How do I tell if the signal in the car is analog or digital?

You can use a multimeter to test car signals. The multimeter can also be used to test voltage, resistance, and current.

The video below of testing signals is for your reference:
https://www.youtube.com/watch?v=n9Obx15AjdM