Onstar loose ground noise
 

Hi everyone,
Newb.
Onstar works sometimes and at other times I get a loose ground sound. Onstar diagnosed came up with nothing. I tightened the battery cables which were very loose, and that seemed to work until I drove home and retested it a few hours later and the noise returned. I live on the Jersey shore, far as I know we get a good signal there. My neighbor has Onstar and has no problems with such a sound. Only the Onstar is affected. Everything else works great. Anyone have any ideas what I can check to fix such a problem?