Any way to disable the USB port so that it only works when the key is in the ignition, or turned on? Not sure if there are any setting somewhere I can access via Data port to disable the USB port in the front dash.




Every time I open a door or unlock my car, even when turned off, it connects my USB/Aux (Tunai Firefly) device to my phone and redirects the audio away from my headphones. Sometimes it happens if I’m just in range of the car and it has recently been shut off.




Is there a fix for this?

 

Instead of plugging your Bluetooth dongle into the USB port, try plugging it into the cigarette lighter (with a USB power adapter). The issue is that the dongle will start up and try to connect whenever it receives power. The cigarette lighter won't have power until you turn on the car. I doubt there is any way to control power to the USB port.

 

I had a similar issue when wiring the aftermarket radio in my 2013 MCS. Initially I tapped accessory power wire to the RAD_ON wire on factory radio and got the same result - the touch screen would turn on as soon as I unlock the car and some times even after it's been locked. Since factory radio can be turned on without car running, equipment running on that circuit can be powered independent of ignition.
I found out with the help of multimeter that the front 12V power socket is powered only when engine is running, so after tapping aftermarket radio's ACC+ to cigarette lighter's positive wire, the touch screen light up the moment I start the engine and turns off when I stop it.
So, as rkw pointed out, your best bet is to plug the Bluetooth dongle into front power socket via adapter.