iPhone TRRS Circuit Not Working

[rocket100]

So basically what I am doing is creating an FSK module that sends data to the iPhone via a 4 pin headphone connector (TRRS). So the FSK audio signal comes from the module, and into the mic pin of the TRRS. Additionally, the iPhone app outputs a tone that is taken from the headphone jack and used to harvest power for the FSK module so it doesn't have to run off of batteries. In order to make the iPhone detect an external microphone input, I've put a 4.7k resistor across the mic and ground rings. It works, but there's a problem. For some reason that causes the audio output power tone to be all distorted coming out of the headphone jack. If I short the mic and ground ring together (effectively turning it into a normal 3 pin headphone connector), the audio comes out nice and clean. Can anybody explain why this is happening? Thanks!!!