Modules

WARNING: PRIOR TO REMOVAL OF ANY SRS MODULES AND BEFORE DISCONNECTING ANY SRS MODULE ELECTRICAL CONNECTORS, THE BATTERY GROUND CABLE SHOULD BE DISCONNECTED AND A PERIOD OF AT LEAST ONE MINUTE ALLOWED TO ELAPSE.


NOTE: The SRS modules do not contain any serviceable components.


The SRS consists of the following module:

Restraints Control Module (RCM)


NOTE: Due to the importance of the RCM being securely fixed to the vehicle body, the ground connection is made via the fixings and is monitored by the diagnostic system.


The RCM is mounted on the top of the drive shaft tunnel below the center console. It identifies crash severity, the direction of impact and makes decisions on deployment of air bag modules and front safety belt pretensioners. It also provides firing signals to all air bag modules and front safety belt pretensioners.

The RCM controls air bag deployment decisions by using signals from its internal accelerometer and the following:
- Front crash sensor
- Occupancy sensors
- Front safety belt buckle sensor
- Driver seat track position sensor
- Front seat passenger weight sensing system
- Occupancy sensing module

Internally, the RCM has two areas that determine which elements of the SRS are to be deployed:
- Crash severity evaluation - This area evaluates crash severity by using data from the RCM internal accelerometer, the front crash sensor and the safety belt buckle sensor. Based on this data, the RCM decides which level of air bag module deployment is required and forwards the information to the second area, the deployment handler.
- Deployment handler - The status of the seat track position sensor, occupancy sensors, front seat passenger weight sensing system and safety belt buckle sensors are examined before a decision is made about which restraints should finally be deployed. For instance, if the occupancy sensing and weight sensing system indicate that the passenger front seat is empty, then no restraint deployment will take place on the passenger side, even if full deployment takes place on the driver side.

Data from the side crash sensors is used by the RCM in conjunction with acceleration data from the RCM internal accelerometer to make a deployment decision. The RCM processes the acceleration data and subject to an impact being of high enough severity, decides whether the side air bag module should be deployed. The decision is forwarded to the deployment handler (within the RCM) which responds appropriately. For example, in the case that the front seat passenger weight sensing system calculates that the seat is empty, or occupied by a small person, the passenger side air bag module will be disabled.

On board testing of the air bag module, front safety belt pretensioner firing circuits, warning indicator circuits and module status (the front and side crash sensors perform basic self-tests) is performed by the RCM together with the storing of fault codes.

The RCM drives the SRS indicator on the instrument pack. If the warning lamp fails, a fault code is recorded and a warning tone is sounded. It also provides a temporary back-up power supply to operate the air bag modules in the event that in crash conditions, the battery supply is lost. In the event of a crash, it records certain data such deceleration information, firing delay and fault codes for subsequent access via the diagnostic connector.

Driver Air Bag Module


NOTE: Variation in the driver air bag module deployment is determined by the timing of the first and second stage ignition signals. This facilitates adaptation of the stiffness and timing of the air bag module to optimize occupant protection.


The driver air bag module is controlled by the RCM which chooses between first or second stage deployment, depending on the occupant position and the crash severity. To reduce the risk of an air bag module induced injury to a driver that is positioned close to the steering wheel, the air bag module deploys radially. It has a non-azide propellant that reduces particulates and effluents. It consists of a twin stage inflator (as opposed to a single stage inflator) with separate chambers for the two inflation stages, each being independently activated by the RCM. It has two air bag electrical connectors that have foolproof mechanical keying and are color coded to the respective connector on the inflator.

Passenger Air Bag Module


NOTE: Variation in the passenger air bag module deployment is determined by the timing of the first and second stage ignition signals. This facilitates adaptation of the stiffness and timing of the air bag module to optimize occupant protection.


The passenger air bag module is controlled by the RCM which chooses between first or second stage deployment, depending on the occupant status and the crash severity. It consists of a twin stage inflator (as opposed to a single stage inflator) with two air bag electrical connectors to accommodate the twin stage inflation.

The heated gas inflator consists of a high-pressure mix of clean air and hydrogen gas, triggered by two separate ignition squibs. It produces a controlled generation of clean gas to rapidly fill the air bag. It is classified as a stored flammable gas (not as an explosive) and as such, has less restrictive storage and transportation requirements. It produces a very clean burn and almost no particulates and is almost free of any toxins, making disposal or recycling much easier.

Side Air Bag Module


NOTE: In the event of a side impact that is sufficient to deploy the side air bag module, it will be necessary to replace the complete seat. The side air bag module does not contain any serviceable components.


The side air bag module is mounted in the outboard bolster of each front seat and uses compressed argon to inflate. It provides protection for the thorax (the part of the trunk between the neck and the abdomen) and head. In an air bag deployment situation, it deploys through the stitch seam in the side bolster. To ensure the air bag always emerges at the same point, a chute is attached to the inside of the trim cover and wrapped around the air bag module.

Occupancy Sensing Module
The occupancy sensing module is located on the right-hand side of the instrument panel. It constantly monitors and processes signals received from the occupancy sensors and makes data available to the RCM, via the CAN network.

Data from the sensors is correlated by the occupancy sensing module and used to decide when the passenger front seat occupant has leaned into an area in front of the passenger air bag deployment door, known as the 'keep-out zone'. The system is sophisticated enough to be unaffected by body extremities (hands and feet) and respond only to head or body movements. When the passenger leans forward into the zone, the system will disable the passenger air bag module and provide visual confirmation by illuminating the PAD indicator.