I have recently owned a used Chevy caprice 1991 . As i am having some problems with my ECM/ECU ( Electronic control Unit), so i am deciding to reset it by un-plugging the battery terminals. I am just not very sure that after re-plugging the battery terminals, would my Ac Delco AM/FM Cassette player requires a UNLOCK Code to starting working ? Its original Delco Radio provided with Chevy caprice 1991. I am not yet sure if that would require an Unlock Code or not. Please help me.