Default Bluetooth Streaming to Car

My car (2014 Toyota) has a2dp media streaming from my note 3. it works fine but one thing is driving me nuts. If I am not streaming music or radio from my phone it just plays samsung installed musack on its own. in the absense of me streaming something it just streams on its own. I do not want this to happen. how can I figure out what app is streaming on its own and prevent it. Sometimes I only want the bluetooth to stream google maps.

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