AIRBAG SYSTEM


  1. FUNCTION OF MAIN COMPONENTS


    1. The main components in the airbag system have the following functions:

      Components Outline
      Airbag ECU Assembly

      • In the event of a frontal collision, the airbag ECU assembly receives signals from either of the front airbag sensors. The airbag ECU assembly receives the signal via its judgment circuit and also receives another signal from the safing sensor built into the airbag ECU assembly. After receiving a signal from at least one of the front airbag sensors and the safing sensor, the airbag ECU assembly determines whether the driver airbag, front passenger airbag, driver knee airbag, front seat cushion airbag, curtain shield airbags, front side airbags, front seat belt pretensioners and rear seat belt pretensioners should be deployed. The airbag ECU assembly also diagnoses system malfunctions.

      • In the event of a side or rear side collision, the airbag ECU assembly receives signals from the door side airbag sensor, side airbag sensor assembly, No. 2 side airbag sensor assembly or rear airbag sensor. The airbag ECU assembly receives the signal via its judgment circuit and also receives another signal from the safing sensor built into the airbag ECU assembly. After receiving a signal from at least one of the side sensors and the safing sensor, the airbag ECU assembly determines whether the front side airbags, curtain shield airbags and front seat belt pretensioners should be deployed. The airbag ECU assembly also diagnoses system malfunctions.

      • Sends an airbag deployment signal to the EV Control ECU and main body ECU (multiplex network body ECU).
      Horn Button Assembly Used as supplements to the seat belts to help reduce impact to the occupants.
      Instrument Panel Passenger Airbag without Door Assembly
      Lower No. 1 Instrument Panel Airbag Assembly
      Front Seat Cushion Airbag Assembly RH
      Front Seat Airbag Assembly LH/RH
      Curtain Shield Airbag Assembly LH/RH
      Front Airbag Sensor LH/RH Based on the deceleration of the vehicle during a frontal collision, distortion is created in the sensor and is converted into an electrical signal.
      Door Side Airbag Sensor LH/RH Based on the deceleration of the vehicle during a side or rear side collision, distortion is created in the sensor and is converted into an electrical signal.
      No. 2 Side Airbag Sensor Assembly LH/RH
      Side Airbag Sensor Assembly
      Rear Airbag Sensor LH/RH
      Front Seat Outer Belt Assembly LH/RH Used to help reduce impact to the occupants
      Rear Seat 3 Point Type Outer Belt Assembly LH/RH
      Front Seat Inner Belt Assembly LH Seat Belt Buckle Switch Detects if the driver seat belt is fastened.
      Front Seat Inner Belt Assembly RH Seat Belt Buckle Switch Detects if the front passenger seat belt is fastened.
      Seat Position Airbag Sensor Detects the slide position of the driver seat.
      Airbag Cut Off Switch Cylinder Sub-assembly The airbag cut off switch cylinder sub-assembly suspends the instrument panel passenger airbag without door assembly and front seat cushion airbag assembly RH operation.
      Combination Meter Assembly SRS Warning Light Turns on to alert the driver when the airbag ECU assembly detects a malfunction in the airbag system.
      AIRBAG ON/OFF Indicator Light Illuminates to inform the occupants whether the airbags and seat belt pretensioner for front passenger are active state or inactive state.
      EV Control ECU Receives an airbag deployment signal from the airbag ECU assembly and shut off the flow of hydrogen fuel to the FC stack and the high voltage power supply circuits from EV battery.
      Main Body ECU (Multiplex Network Body ECU) Receives an airbag deployment signal from the airbag ECU assembly and operates the collision door lock release function.

  2. SYSTEM CONTROL


    1. Airbag for Frontal Collision


      1. There are 8 airbags which deploy in the event of a frontal collision: the horn button assembly, instrument panel passenger airbag without door assembly, lower No. 1 instrument panel airbag assembly, front seat cushion airbag assembly RH, front seat airbag assemblies and curtain shield airbag assemblies. These airbags deploy simultaneously. The horn button assembly and instrument panel passenger airbag without door assembly use dual-stage control. In addition, the front pretensioners contained in the front seat outer belt assembly LH and RH, and rear pretensioners contained in the rear seat 3 point type outer belt assembly LH and RH are also activated.

      2. The airbag ECU assembly detects the information indicated below from various sources in order to activate the dual-stage control.

      3. For a frontal collision, if a front airbag sensor detects an impact, it informs the airbag ECU assembly. The airbag ECU assembly causes the horn button assembly, instrument panel passenger airbag without door assembly, lower No. 1 instrument panel airbag assembly, front seat cushion airbag assembly RH, front seat airbag assemblies and curtain shield airbag assemblies to deploy. Meanwhile, the airbag ECU assembly activates the front seat belt pretensioners and rear seat belt pretensioners.

        A01MA78E01

      4. Deceleration sensors used for the SRS airbag system are installed on various parts on the vehicle and calculate the deceleration (or acceleration) rate of each part during a collision.

      5. Depending on the situation, the airbag ECU assembly sends a deployment signal to each airbag based on the information from each sensor.

      6. Frontal collision signals are produced based on the information from the airbag ECU assembly and front airbag sensors. Frontal collision signals are used to deploy the airbags and activate the pretensioners as indicated in the table below.

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    2. Airbag for Side/Rear Side Collision


      1. There are 2 airbags which deploy in the event of a severe side collision: the front seat airbag assembly and curtain shield airbag assembly. These airbags deploy simultaneously. Additionally, at the same time, the front seat belt pretensioners is also activated.

      2. For a side collision, if the door side airbag sensor, side airbag sensor assembly and No. 2 side airbag sensor assembly detects an impact, it informs the airbag ECU assembly, and the airbag ECU assembly causes the front seat airbag assembly and curtain shield airbag assembly to deploy simultaneously, and activates the front seat belt pretensioners.

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      3. The front seat airbag assembly and curtain shield airbag assembly are deployed and the front pretensioner in the front seat outer belt assembly LH or RH is activated based on signals from the door side airbag sensors, side airbag sensor assemblies, No. 2 side airbag sensor assemblies and airbag ECU assembly.

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      4. For a rear side collision, if the rear airbag sensor and No. 2 side airbag sensor assembly detects an impact, it informs the airbag ECU assembly and the airbag ECU assembly causes the curtain shield airbag assembly to deploy.

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      5. The curtain shield airbag assembly is deployed based on signals from the rear airbag sensors, No. 2 side airbag sensor assemblies and airbag ECU assembly.

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    3. Primary Check Illumination Control


      1. After the power switch is turned on (IG), the airbag ECU assembly illuminates the SRS airbag warning light in the combination meter assembly for approximately 6 seconds and conducts the primary check. During the primary check, the ignition of airbags is prohibited and a diagnosis of the airbag ECU assembly is performed. If a malfunction is detected during the primary check, the SRS airbag warning light remains on even after the 6 seconds have elapsed.

      2. After the power switch is turned on (IG), the airbag ECU assembly operates the passenger AIRBAG ON/OFF indicator lights as shown below to check for an open in the indicator light circuits.

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  3. DIAGNOSIS


    1. If the airbag ECU assembly detects a malfunction in the SRS airbag system, the airbag ECU assembly stores the malfunction data in memory in addition to illuminating the SRS airbag warning light.

    2. The airbag ECU assembly outputs malfunction data and 5-digit Diagnostic Trouble Codes (DTCs) to the Global TechStream (GTS).

    3. The 5-digit DTCs can be read after connecting the Global TechStream (GTS) to the DLC3. For details, refer to the Repair Manual.

    4. If the SRS airbags deploy, the airbag ECU assembly will turn on the SRS airbag warning light. However, unlike the ordinary diagnosis function, a DTC will not be stored. The SRS airbag warning light cannot be manually turned off. It is necessary to replace the airbag ECU assembly with a new one.