Inspection Procedure 6: Vehicle power cannot be turned OFF when the shift position is in "P". (Power supply mode ON to ACC is possible): Notes
WARNING: This page is about a different car, the 2014 Mitsubishi Outlander. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION:
Before replacing the ECU, ensure that the power supply circuit, the ground circuit and the communication circuit are normal.