Connecting steering wheel controls to the car radio

I'm trying to install a Chinese double-DIN radio into a Toyota Prius. The old, original CD changer was defective.

After removing the original radio, initially, a portion of the system bus stopped working – including the air conditioning, etc. I resolved this issue by adding a 100-ohm termination resistor.

Okay, now I want to connect the steering wheel buttons to the new radio. It seems like there are two wires responsible: "Key1-5Volt" and "Key2-5Volt". The original connector has 5 pins connected: red, black, white, pink, white.


I've tried all possible combinations. Except for a system error message, nothing happens. My thought is that the pink-white wire must be the CAN bus because the termination resistor affects the system. Then, key1 and key2 probably connect to those pins? With a termination resistor?

I am grateful for any help.

Sure, here is the translation of the text from German to English:

"foto dazu"

"photo of it"

The steering wheel control panel/car radio reacts to pink when connected to key1 and white when connected to key2. However, the buttons are not yet working. I suspect that the termination resistor is not connected correctly, which is why the signal is too weak. How do you do it right?

The CAN bus is typically terminated with 120 ohms, but I'm not sure what that has to do with the two wires connected to the buttons...

Best regards, Rainer.

I've been wondering the same thing. The cables labeled "Key1/2" come from the car stereo. Since there's a learning monitor, there must be a digital signal going into them. I assume that the steering wheel buttons are connected via the CAN bus, so key1/2 need to be connected to the CAN bus.

Unfortunately, the manual is not really helpful.

leluno wrote:

I'm wondering the same thing. The cables labeled with Key1/2 come from the car radio. Since there's a learning monitor, there must be a digital signal going into it. I assume that the steering wheel buttons are connected via the CAN bus, so key1/2 need to be connected to the CAN bus. The manual is unfortunately not really helpful.

Certainly not.

I've now found a wiring diagram for the Prius. The steering wheel buttons are simply buttons that switch resistors to ground (?). It has nothing to do with CAN bus.

That sounds like a nice little project for Christmas: connecting steering wheel buttons to an Arduino, which then sends the signals to the car radio via CAN.

The steering wheel buttons can be connected directly to the radio without an adapter. However, I had already ordered an Arduino CAN shield/MCP2515. There are a few things about my car that have been bothering me for a long time:

-The heating system should automatically shut off when the vehicle is stationary, so that the engine turns off.
-In cold temperatures, the windows would need to be slightly open to prevent them from freezing shut.
-The passenger-side mirror should tilt downwards when the reverse gear is engaged.

Maybe this is something perfect for Christmas.