A transport refrigeration system controller-to-engine control unit interface (200, 300, 400, 500) for a TRS of a refrigerated transport unit comprising: a TRS controller (205, 305, 405, 505) programmed to regulate operating conditions within the refrigerated transport unit; an ECU (210, 315, 415, 515) of an electronically controlled engine (215, 310, 410, 510) configured to provide power to the TRS, wherein the ECU (210, 315, 415, 515) is programmed to control the electronically controlled engine (215, 310, 410, 510); a controller area network communication connection (230, 330, 430, 530) between the TRS controller (205, 305, 405, 505) and the ECU (210, 315, 415, 515), wherein the CAN communication connection (230, 330, 430, 530) is configured to facilitate two way communication between the TRS controller (205, 305, 405, 505) and the ECU (210, 315, 415, 515); and characterised by a keyswitch connection (220, 320) between the TRS controller (205, 305, 405, 505) and the ECU (210, 315, 415, 515), the keyswitch connection (220, 320) being configured to enable the ECU (210, 315, 415, 515) for an engine sub-system operation, wherein when the keyswitch connection (220, 320) is in an active logic state, the keyswitch connection (220, 320) is configured to enable communication between the TRS controller (205, 305, 405, 505) and the electronically controlled engine (215, 310, 410, 510) via the ECU (210, 315, 415, 515), and when the keyswitch connection (220, 320) transitions from an active logic state to an inactive logic state, the ECU (210, 315, 415, 515) is configured to enter a power latch stage and command a pre-shutdown component calibration of the electronically controlled engine (215, 310, 410, 510). a TRS controller (205, 305, 405, 505) programmed to regulate operating conditions within the refrigerated transport unit; an ECU (210, 315, 415, 515) of an electronically controlled engine (215, 310, 410, 510) configured to provide power to the TRS, wherein the ECU (210, 315, 415, 515) is programmed to control the electronically controlled engine (215, 310, 410, 510); a controller area network communication connection (230, 330, 430, 530) between the TRS controller (205, 305, 405, 505) and the ECU (210, 315, 415, 515), wherein the CAN communication connection (230, 330, 430, 530) is configured to facilitate two way communication between the TRS controller (205, 305, 405, 505) and the ECU (210, 315, 415, 515); and characterised by a keyswitch connection (220, 320) between the TRS controller (205, 305, 405, 505) and the ECU (210, 315, 415, 515), the keyswitch connection (220, 320) being configured to enable the ECU (210, 315, 415, 515) for an engine sub-system operation, wherein when the keyswitch connection (220, 320) is in an active logic state, the keyswitch connection (220, 320) is configured to enable communication between the TRS controller (205, 305, 405, 505) and the electronically controlled engine (215, 310, 410, 510) via the ECU (210, 315, 415, 515), and when the keyswitch connection (220, 320) transitions from an active logic state to an inactive logic state, the ECU (210, 315, 415, 515) is configured to enter a power latch stage and command a pre-shutdown component calibration of the electronically controlled engine (215, 310, 410, 510).