Trouble Judgment
WARNING: This page is about a different car, the 2015 Mitsubishi Lancer. However, it is still accessible from the selected car via links, so may be relevant.
DTC U0019 will be stored when the A/C controller assembly (A/C-ECU) or heater controller assembly (A/C-ECU) (vehicles without A/C) ceases CAN communication (bus off) and then resumes the communication when the ignition switch is turned to the "LOCK" (OFF) position.