Precautions For Removing Battery Terminal

With the adoption of Auto ACC function, ACC power is automatically supplied by operating the Intelligent 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 in the OFF position, i.e. ACC power is supplied for a certain fixed time.
When disconnecting the 12 V battery terminal, place the ignition switch in the OFF position before disconnecting the 12 V battery terminal, observing "How to disconnect 12 V battery terminal" described below.

Courtesy of NISSAN

NOTE: Some ECUs operate for a certain fixed time even after ignition switch is in the OFF position 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 two batteries, be sure to connect the main battery and the sub-battery before placing the ignition switch in the ON position.
NOTE: If the ignition switch is in the ON position with any one of the terminals of main battery and sub-battery disconnected, then DTC may be detected.
After installing the 12 V battery, always check "Self Diagnosis Result" of all ECUs and erase DTC.
NOTE: The removal of 12 V battery may cause a DTC detection error.