• First ask if OEM sound works before installation.
  • If no, fix OEM sound first.
  • If yes, continue below.
• Go to 'settings', 'equalizer' settings of the PX6 unit. Resetting the balance.
• Make sure you have connected the AUX cable to your vehicle's AUX port, like the picture below. The other end of the cable does not need to be connected.
  
• Use steering wheel control to adjust volume and switch to OEM FM radio to make sure it has sound. Then, while the android unit is playing aftermarket sound, use steering wheel control to switch to OEM AUX audio source. Please refer to this video. https://youtu.be/KMB62bQaqjQ
• If the gauge cluster/speedometer shows 'audio off', or OEM FM radio does not have sound, make sure you did not remove or disconnect OEM radio or disc player. Only OEM screen and AC control panel are to be removed during installation. You can restore factory connections. If it's still the same, you need to check fuse or fix factory audio first.
• If AUX port is plugged in but AUX source not available for selection with steering wheel control, you may have to replace OEM USB/AUX module. However, you can first try disconnecting battery negative cable and reconnecting after several minutes to reinitialize the radio/HMI to see if AUX can then be deteced.
  
  
• If you performed above steps and the AUX source is selected, but android sound still not available, then you need to check the connection at the back of the unit. Make sure you have connected the T-harness and the audio box. The T-harness is connected between the OEM radio and the gray OEM radio connector. The yellow and black connector from the audio box are connected to the back of the PX6 unit:

• If above all checks out but still no sound, then the unit, the harness, or the audio box is defective.