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Toyota Sienna Service Manual: System description

1. GENERAL

  1. In conjunction with impact absorbing structure for a frontal collision, the SRS (Supplemental Restraint System) driver airbag and front passenger airbag were designed to supplement seat belts in the event of a frontal collision in order to help reduce shock to the head and chest. This system is a 3-sensor type airbag system to detect the impact during a frontal collision using the center airbag sensor assembly and front airbag sensors. It also operates the airbag system and seat belt pretensioner.
  2.  In order to detect the extent of the collision during the initial stages of the collision in further detail, the front airbag sensors have been changed from mechanical type to electrical type deceleration sensors. Accordingly, the deployment of the driver airbag and front passenger airbag is controlled in two stages according to the severity of the impact.
  3.  In conjunction with impact absorbing structure for a side collision, the front seat side airbag and curtain shield airbag were designed to help reduce shock to the driver, front passenger, and rear outer passengers in the event of a side collision or rollover.
  4.  RSCA (Roll Sensing of Curtain Shield Airbags) is used in order to deploy the curtain shield airbags and the seat belt pretensioner for the driver and front passenger, in the event that the vehicle rolls over.
  5.  The curtain shield airbag that helps reduce shock to the front and rear seat occupants with a single curtain shield airbag has been adopted. In conjunction with this system, the side airbag sensors have been installed at the bottom of the center pillars and the rear airbag sensors have been installed at the bottom of the rear pillars respectively.
  6.  In this system, a front side collision is detected by the side airbag sensors in order to deploy the front seat side airbag and curtain shield airbag. A rear side collision is detected by the rear airbag sensors and the center airbag sensor assembly in order to deploy the curtain shield airbag.
  7.  The center airbag sensor assembly sends the airbag deployment signal to the ECM through BEAN (Body Electronics Area Network) and CAN (Controller Area Network) to operate the fuel pump control.
  8.  The center airbag sensor assembly sends the airbag deployment signal to the body ECU via a discrete line to operate collision door lock release control.

2. CONSTRUCTION AND OPERATION

  1. FRONT AIRBAG SENSOR
  1.  The front airbag sensors are installed on the right and left radiator supports respectively.
  2.  The front airbag sensor uses an electrical type deceleration sensor.
  3.  The deceleration sensor is built into the front airbag sensor, and the distortion that is created in the sensor is converted into an electric signal based on the vehicle deceleration rate during a frontal collision. Accordingly, the extent of the initial collision can be detected in detail.
  1.  SIDE AIRBAG SENSOR
  1.  The side airbag sensors are installed on the bottom of the right and left center pillars respectively.
  2.  The side airbag sensor uses an electrical type deceleration sensor.
  3.  The deceleration sensor is built into the side airbag sensor, and the distortion that is created in the sensor is converted into an electric signal based on the vehicle deceleration rate during a front side collision. Accordingly, the extent of the initial collision can be detected in detail.
  1.  REAR AIRBAG SENSOR
  1.  The rear airbag sensors are installed on the right and left rear pillars respectively.
  2.  The rear airbag sensor uses an electrical type deceleration sensor.
  3.  The deceleration sensor is built into the rear airbag sensor, and the distortion that is created in the sensor is converted into an electric signal based on the vehicle deceleration rate during a rear side collision. Accordingly, the extent of the initial collision can be detected in detail.
  1.  CENTER AIRBAG SENSOR ASSEMBLY
  1.  General
  1.  Deceleration sensor and ignition control circuit
  1.  Safing sensor
  1.  Backup power source
  1. Diagnostic circuit
  1.  Memory circuit
  1.  SRS WARNING LIGHT
  1.  The SRS warning light is located on the combination meter assembly. It comes on to inform the driver of system trouble when a malfunction is detected in self-diagnosis of the center airbag sensor assembly. Under normal operating conditions, when the ignition switch is turned to the ON position, it comes on for approximately 6 seconds and then goes off.

3. DEPLOYMENT CONDITION

When the vehicle collides and the shock is greater than the specified value, the SRS is activated automatically.

The center airbag sensor assembly includes the safing sensor and deceleration sensor. The safing sensor was designed to be turned on at a smaller deceleration rate than the deceleration sensor.

  1.  The center airbag sensor assembly determines whether or not ignition is necessary based on signals from the deceleration sensor and the front airbag sensor (*1). If the safing sensor and deceleration sensor turn on simultaneously, current flows to the squibs to deploy the SRS as shown in the illustration below.

DEPLOYMENT CONDITION

HINT: *1: In case of a front collision, the ignition signal could be output with the deceleration sensor ON signal even without a signal from the front airbag sensor.

  1. The center airbag sensor assembly determines whether or not ignition is necessary based on signals from the side airbag sensor. If the safing sensor and side airbag sensor turn on simultaneously, current flows to the squib to deploy the SRS as shown in the illustration below.

DEPLOYMENT CONDITION

  1. The center airbag sensor assembly determines whether or not ignition is necessary based on signals from the rear airbag sensor. If the safing sensor and rear airbag sensor turn on simultaneously, current flows to the squib to deploy the SRS as shown in the illustration below (*1).

DEPLOYMENT CONDITION

HINT: *1: If the front seat side airbag assembly deploys, the curtain shield airbag assembly will also deploy, regardless of whether the signal is output from the rear airbag sensor.

  1. The vehicle is equipped with the function to activate the SRS in case of vehicle rollover. A circuit to detect vehicle rollover is built into the center airbag sensor assembly. When the conditions for vehicle rollover are met, the SRS is activated as shown in the illustration below.

DEPLOYMENT CONDITION

Parts location
System diagram ...

How to proceed with troubleshooting
HINT: *: Use the intelligent tester. 1 VEHICLE BROUGHT TO WORKSHOP 2 CUSTOMER PROBLEM ANALYSIS (a) Confirm problem symptoms 3 CHECK MULTIPLEX COMMUNICATION SYSTEM* Check if the multi ...

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Voice Guidance does not Function
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