Diagnosis System [06/2020 - ]

1. The battery ECU assembly has a self-diagnosis system. If the computer, hybrid control system, or a component is not working properly, the ECU records the conditions that relate to the fault. The ECU also illuminates the master warning in the combination meter assembly and provides other appropriate messages on the multi-information display, such as the HV system warning message, HV battery warning message, or discharge warning message.

• When troubleshooting OBD II (On-Board Diagnostics) vehicles, the Techstream (complying with SAE J1978) must be connected to the DLC3 (Data Link Connector 3) of the vehicle. Various data in the vehicle ECM (Engine Control Module) can then be read.
• OBD II regulations require that the vehicle's on-board computer illuminates the MIL (Malfunction Indicator Lamp) on the instrument panel when the computer detects a malfunction in:

  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

  1. The emission control system components.
  2. The powertrain control components (which affect vehicle emissions).
  3. The computer itself.

     In addition, the applicable DTCs prescribed by SAE J2012 are recorded in the battery ECU assembly memory. If the malfunction does not recur in 3 consecutive trips, the MIL turns off automatically but the DTCs remain recorded in the battery ECU assembly memory.

• To check for DTCs, connect the Techstream to the DLC3. The Techstream displays DTCs, freeze frame data, and a variety of hybrid control system data. The DTCs and freeze frame data can be cleared with the Techstream. In order to enhance the OBD function on vehicles and develop the off-board diagnosis system, Controller Area Network (CAN) communication is used in this system. CAN is a network which uses a pair of data transmission lines spanning multiple computers and sensors. It allows for high speed communications between the systems and simplification of the wire harness connections.

Following is the description for storage of DTC using "2 trip detection logic". 

1. When a malfunction is first detected, the malfunction is temporarily stored in the battery ECU assembly memory (1st trip). If the same malfunction is detected during the next drive cycle, the MIL is illuminated (2nd trip).

1. The battery ECU assembly records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was moving or stationary, whether the engine was warmed up or not, as well as other data recorded at the time of a malfunction.

Standard Voltage

1. If voltage is below 11 V, replace or recharge the auxiliary battery.
   NOTE:

   After turning the ignition switch off, waiting time may be required before disconnecting the cable from the negative (-) auxiliary battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) auxiliary battery terminal notices before proceeding with work.

   Refer to PRECAUTION [11/2018 - ]

1. The MIL is illuminated when the ignition switch is first turned to ON, before the READY light comes on.
2. When the READY indicator turns on, the MIL should turn off. If the MIL remains illuminated, the diagnosis system has detected a malfunction or abnormality in the system.

   HINT: 

   If the MIL is not illuminated when the ignition switch is first turned to ON, check the MIL circuit.

   for SFI System: Refer to MIL Circuit [02/2019 - 08/2020] , or refer to MIL Circuit [08/2020 - 10/2022] , or refer to MIL Circuit [10/2022 - ]