Different type of audio signal?

Hello,

I'm trying to install an AUX input and a bluetooth module in my car audio system. (Lexus ES330, Pioneer)

I succeeded connecting AUX cable by connecting the cable into 3 pins in the first picture.

It was easier than I expected it to be because when I select Tape In, it played the cassette tape, and automatically changed source when I put the cable into my iPhone. (it made successive bursting sounds when connected and not playing music with iPhone though)

I expected installing a bluetooth module to be as easy but it wasn't.

The bluetooth receiver has its own input and output pins. When bluetooth is not connected, input cable signal bypasses through the module. When bluetooth is connected, it mutes the input cable signal and plays the bluetooth signal.

Here's the problem I got:

I wired the bluetooth module between iPhone cable and the audio system. When bluetooth is not connected, source from iPhone cable is played as expected. However, when I connect bluetooth, the audio system change the source to cassette tape.

I have no idea why this happens. 3 pins in the first picture only recognize iPhone signal, but not the signal from the bluetooth module. Is there a difference between those 2 signals? Maybe voltage difference? I really need your help here.

For the reference, I attached the circuit board for the audio system. CN300 is the 3 pins that I connected the cable to.

Thank you in advance!

Best,

Pak





View attachment Circuit Board.pdf