The MIC module is located and mounted at the bottom of the PCB board layout. near the antenna terminal contact pins.There are four components being mounted near to it and this are composed of filter coils and an ESD protection resistor or capacitors.
Nokia C1-01 MIC - microphone mouthpiece Solution
You may check the filter coils first, if the coils is open or already busted replaced it.If the filter coils were okay you proceed to replace the MIC module if found damaged.