Microphone not working when plugged to AUX on iPhone 16 Pro

If you are still having this issue I believe the problem is the dongle that you use. If the USB C to 3mm dongle supports both audio and microphone, ie for use with headphones that have an integral microphone that allows you to take call, then it won't work for use in a car aux in situation. This type of dongle disables the microphone on the phone. You need to use an audio-only dongle. Then, when plugged into the aux of the car the phone mic is still active and will allow voice on the call to go thru.