2005 Ion Saturn

Having problems with intermittent electrical activities while going down the road, such as door locks opening and closing repeatably, horn going off, wipers trying to start up, flasher lights going off, and once total shut down of everything. signal lights, horn etc. Doesn’t seem to affect the engine or transmission, just the other electrical items. A local shop thinks there is a bad ground somewhere. Can’t get it to read out on his dignostic machine. Any help out there that might help me resolve the issue?