Answer to: No sound or mic during calls only."FIXED"I had this same problem my S4 phone will dial but no sound no mic. But when i hooked it up to blue tooth it worked threw my blue tooth device. I took it apart checked all my connections made sure everything was connected still no sound no mic. So i bought a new phone but it still bothered me that my old phone was not working properly since i had nothing to loose i took my old phone apart removed the main board removed camera lens that was attached all down to the bare board . Then i heated up my toaster oven as hot as i can get it . Placed main board flat on a piece of parchment in oven for 8 min . Took it out let it cool down put it all back together and now my old phone works perfect. I'm guessing that there must have been a bad soldering spot on the board and the heat from the oven fixed it. Been 3 days and it still works perfect.