while driving, your alternator should be the source for electricity... i had this same prob...
under warranty dealer replaced alternator.... symptoms went away and came back
they then changed "intergrated supply (module: 121099)
as well as 322 IPS which is a position sensor fro tranny
says test for DME faults - all faults led to "IVM powering up modules" they checked power and ground to IVM had voltage drop Replaced IVM.