I had a system installed in my f150 and it had static.. they tried a few things and determined one of the causes may be a bad head unit ground. Where is the stock head unit grounding location? I have a 2011 f150 with the non sony system. Any help would be appreciated.

 

mine just has a black ground wire in the wire harness, but really, you could ground to any metal surface. just check it with multimeter.