Precautions For Removing Battery Terminal: Notes

With the adoption of Auto ACC function, ACC power is automatically supplied by operating the Keyless operation key or remote keyless entry or by opening/closing the driver side door. In addition, ACC power is supplied even after the ignition switch is turned to the OFF position, i.e. ACC power is supplied for a certain fixed time.
When disconnecting the 12V battery terminal, turn off the ACC power before disconnecting the 12V battery terminal, observing "How to disconnect 12V battery terminal" described below.

Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

NOTE: Some ECUs operate for a certain fixed time even after ignition switch is turned OFF and ignition power supply is stopped. If the battery terminal is disconnected before ECU stops, accidental DTC detection or ECU data damage may occur.
For vehicles with the 2-batteries, be sure to connect the main battery and the sub battery before turning ON the ignition switch.
NOTE: If the ignition switch is turned ON with any one of the terminals of main battery and sub battery disconnected, then DTC may be detected.
After installing the 12V battery, always check the DTC of all ECUs and erase DTC.

NOTE: The removal of 12V battery may cause a DTC detection error.