As soon as the switch is turned to the on position, the PCM (Power Train Control Module) makes a check of the charging, battery, and starting system. When the engine is running, the PCM expects to see 13.8 to 14.4 volts in the system. If the voltage is within that range, the system is fully functional.
If the reading is below or above that range, the Check Engine light illuminates and the DTC code P0560 OBDII is set.