Hi Stoked
Thank you for reaching out! I’m sorry to hear about the sound issue you’re experiencing with your Mazda 3. If your vehicle is equipped with a Bose sound system, it requires a specific harness and CANBus adapter to ensure proper audio output.
Please send me a picture of the backside of your factory radio’s plug/connector and a picture of your factory radio screen. I will confirm your car configuration

We appreciate your understanding and time. Looking forward to your reply.
Have a nice day!
Best regard,
Leo