does it happen only after its warmed and then you turn the car off and back on? if so o think its an 04+ voltage regulator thing nothing to do with radio unless if pulls massive current
He's also getting flickering lights and other issues indicating its not just a false message. He needs to watch his voltage and see what is going on.
2011 Mitsubishi Lancer GTS - DD mode
1991 Mitsubishi 3000GT - Many mods to come