Ques. I have a Lenovo K3 Note. It works fine for most part except when i connect it to my car's aux port. I am able to hear the voice of caller but my voice isnt going through. Once i remove the aux cable, everything works fine.
In smart phones mic and headphone jack is same. So when you connect the aux port to car's audio system the phone detects it as a head phone and aspects it to have a mic. So all the audio output and input is delivered and received through aux port.
Since car's audio system does not support mic and voice feed back, you are forced to remove the aux cable at the time of call.