While cruising , check engine and battery warning lights come on. Volts drop down from approx. 15 to 12. Continuing to drive corrects itself : warning lights extinguish and volts come back up to about 15. This happened 3 times today.Shows DTC code P0562 although battery shows 13.4 volts. P0562 is Battery Voltage Low EFI. Anybody any ideas? Thanks. Chief.