Amp PRO Overview and Troubleshooting

Very often we get tech inquiries about problems that arise after an AP4 is installed. However 99% of the time, the AP4 isn't the problem at all. Realistically, an AMP PRO is a very simple device that does not interfere with the vehicles infotainment data-bus at all. To break it down a bit further, the Amp PRO does these things:

• It takes the fixed level, two channel audio signal that goes from the factory radio to the factory amplifier, sends it through a DSP chip to clean it up, then provides a variable Front, Rear, and Non-Fading output to easily feed aftermarket amps.
  • Alternatively, you can also use the APA-TOS1 to acquire a purely digital TOSLINK output, or as most call it "Fiber Optic". When using this type of output, the Amp PRO's DSP chip converts the analog audio signal to digital.
• It "listens" to the vehicle's infotainment data bus for the following commands:
  • Volume +/- adjustments
  • Bass/Mid/Treble audio adjustments
  • Balance/Fader adjustments

That's it! Of course there are 2 exceptions to this that I will detail below, but as you can see, the Amp PRO is not intrusive at all into the vehicles infotainment systems. Here is an illustration to help you understand further.

The two exceptions:

• AP4-GM61 - Instead of tapping into a two channel fixed level audio signal, this module extracts the audio from the M.O.S.T data bus. This module comes equipped with an APA-TOS1 as the audio signal it is tapped into is already digital.
• AP4-CH41 R.2 - When used in vehicles that are not equipped with a factory amplifier, and DIP switch 4 is set to the On (down) position, the module "tricks" the radio into thinking that there is a factory amplifier present, therefore making it behave as such. This AP4 is the only one that actually does any filtering of the vehicle's infotainment bus. That does not imply, however, that this AP4 is anymore complex or intrusive as the others. It simply transits one smal ID to the radio to make the flip.

AP4 Known Issues and Troubleshooting

As of the date this article was written, there is only ONE "known issue" with the AP4 line. 

• The pins which are located in the white harness that connects to the module itself sometimes become dislodged and back out. How to tell if you are having this issue is outlined in detail in this article.
• If you feel you are having an issue with your factory system that is attributed to the Amp PRO, here are a few things you can do to eliminate the interface as the source of the probelm:
  • If using an AP4-CH41 R.2 - Is the factory radio turning on?
    • If yes proceed to the next step.
    • If not, please refer to this article about the loose pins.
  • Does the red LED on the module blink rapidly when you roll the volume knob on the factory radio?
    • If yes, proceed to the next step.
    • If no then answer these questions:
      • Does the vehicle have a factory amplifer?
        • If no then the Amp PRO is not compatible
        • If yes, then further troubleshooting with assistance from our tech department may be needed.
      • If using the AP4-CH41 R.2, did you do the required double sleep cycle as outlined in the instruction manual (Page 2, step 6d)?
        • If yes, try again, but this time let the vehicle sit for 20 minutes each time.
        • If no, please do so.

If you have gone through this entire troubleshooting process and are still having issues. Please contact our tech support department using the support widget in the bottom right corner of this website.