I notice when I use my Iphone 6s (in a call) paired with the car speakers the sub woofer automatically turns off, to improve the audio in a call I bet. Sometimes it glitches; when the call is ended and you turn music back on the sub woofer will not turn back on. The system plays the music but without sub woofer bass. This has only happened twice in 10,500 miles. I figured out the fix today, just reset the main display screen and the sub woofer will come back on. To reset the screen press in both roller wheels on the steering wheel and hold them in until the display goes black (10 secs) then release and it will reload/restart after a min or two. I did this while driving no problem, just no screen for a couple min. This fixes the sub woofer issue. Bill