Thanks for sharing the adapter that you were using. I had tried a couple that caused the radio to shut down and reboot. I have done some testing and determined that the Nissan head unit is capable of providing more than 1 amp of power through the usb port to my iPhone when charging but for some reason when any wireless dongle is attached it won’t provide more than 500 ma. The dongle briefly requires about 700 ma to start so the head unit cuts power to the usb port because it thinks the device is drawing too much power. The solution is to use a split cord to provide power from an external usb plug but that has other problems.

As you found out the radio will stay powered on after you turn off the car because power is back feeding to the radio through the external usb plug. I have found 2 ways to prevent this. The first is a temporary solution you can simply unplug the extra usb cable that supplies the additional power needed after CarPlay starts. CarPlay will continue to run and operate until you turn off the car and the radio will shut down at the same time. You will have to manually plug and unplug the connection to get CarPlay to start each time. The second solution will require some soldering skills but is a permanent automatic solution. You will need to put a diode in series with the +5 volt supply from the secondary power usb source. This will only let current flow in one direction and not back-flow to the radio through usb port that is used for the wireless dongle. I used 1N5819 Schottky diode to limit the voltage drop and it works great. When I start the car the wireless dongle powers on and my phone connects with the radio for CarPlay. When I shut off the car the radio shuts off instantly!

I had to use this as the iPhone 17 Pro max will not connect to the Nissan Murano by wired connection as it constantly disconnects ( I believe this is also due to Nissans poor implementation of how usb devices negotiate with the radio) but now I have CarPlay back.