You have to follow the directions exactly how it’s written, no deviation… or your sound will not be right.
I repeat… to a T… cross I’s and all… if you thin, you’ll get more power or sound by not setting to 0, you are fooling yourself… trust me…
WHEN INSTALLING IN A JBL-EQUIPPED CAR:
Step 1: Before removing the stock radio, turn to FM and turn up the volume to level 45 (yes, 45.) Set Bass, Mid, Treble, Fade, Balance all to 0 (zero). Let that stay on for about 5 seconds, then turn off the radio, then the car. Now, you can remove the stock radio.
Step 2: Install the JBL harness and the Android radio, but do not turn on yet.
Step 3: VERY IMPORTANT: To prime the JBL system to work properly with the new radio do the following: Turn the car to ‘ON’ for 2-3 seconds, then quickly turn the car OFF. Do this step 2 times in a row. (Note: you may not see the radio screen turn on. That’s okay.)
After you complete these steps, your JBL system is properly primed and ready to go! If you did not do this, you’re audio playback will sound like crap. You will notice a huge difference. I pulled these instructions from the Rosen JBL adapter install.