Normally, battery voltage fluctuates from 11.5V to 14.5V. Especially at cranking, voltage can drop to 9.8V. Therefore, actuators which require 12V power supply meet fluctuation of power by 5V. A little change of voltage supply can shift controlling characteristic of actuators, such as injectors, RPV and EGR actuator, which should be controlled delicately. To correct controlling characteristic change arrived from voltage fluctuation, ECM performs actuator operating correction according to voltage change as detecting battery voltage change.

P0563 is set when battery voltage above 17.3V is detected for more than 5 sec.. Check alternator component. (overcharging of alternator)

→ECM senses battery voltage as monitoring the voltages in "Engine control relay ON" terminal.