4WD-ECU



FUNCTION


The main functions of 4WD-ECU are as follows:

  1. Communication function

  • Coupling control function

  • ECU self-diagnosis function


  • FAIL-SAFE FUNCTION



    FAILURE DETECTION


    4WD-ECU performs the following checks at a timing shown in the chart below. 4WD-ECU determines the malfunction occurred when the failure detection conditions are met, and it sets the diagnosis code and executes the countermeasures for trouble. When the failure resume conditions are met, ECU determines the status is normal, and resumes the system.
    note For the fail-safe specification, refer to Workshop Manual.
    Start-up (Initial check just after the ignition switch is turned ON.)
    1. CPU check

  • Actuator check

  • Always (During ignition ON status other than initial check operation)
    1. CPU check

  • Power supply check

  • Actuator check

  • External wire connection check


  • DIAGNOSTIC FUNCTION


    4WD-ECU has the following functions for easier system checks. All of the following items can be diagnosed using the M.U.T.-III.


    DIAGNOSIS CODE SET


    Using M.U.T.-III, the diagnosis code (information of failures generated in the electronically controlled 4WD system) can be read. When a failure occurs, 4WD-ECU sets the diagnosis code for that failure in the nonvolatile memory (EEPROM*), so the recorded information will not be erased even if the battery is disconnected.
    note
    • *EEPROM (Electrical Erasable & Programmable ROM): Special type of memory that can be programmed or erased electrically
    • For the diagnosis code output items of the electronically controlled 4WD, refer to Workshop Manual.

    SERVICE DATA OUTPUT


    Using M.U.T.-III, the data (input data from each ECU and switch) used for control by the electronically controlled 4WD system can be read.
    note For each service data item, refer to Workshop Manual.

    ACTUATOR TEST


    M.U.T.-III can forcibly drive the actuators (electronic control coupling solenoid and drive mode indicator) controlled by the electronically controlled 4WD system.
    note For the actuator test specification, refer to Workshop Manual.

    FREEZE FRAME DATA OUTPUT


    M.U.T.-III can read the freeze frame data (driving conditions when the failure occurs) set when the diagnosis code is detected.
    note For freeze frame data items, refer to Workshop Manual.