Part 1
Air Bag Systems
COMPONENT LOCATION - SHEET 1 OF 2
COMPONENT LOCATION - SHEET 2 OF 2
GENERAL
The SRS (supplemental restraint system) provides additional protection for occupants in certain vehicle accident conditions. The SRS (supplemental restraint system) consists of:
- A driver air bag
- A passenger air bag
- A side air bag on each front seat
- Side air curtains for first and second row seats
- Side air curtains for third row seats (where fitted)
- A pretensioner for each front safety belt
- A buckle sensor for each front safety belt
- Front and side impact sensors
- A passenger air bag deactivation indicator
- A passenger air bag deactivation switch (all except NAS and Australia)
- An occupant monitoring system for the front passenger seat
- A position sensor for the driver seat
- A SRS (supplemental restraint system) warning indicator
- A clockspring
- A RCM (restraints control module).
WARNING: WARNING:All pyrotechnic devices are dangerous. Before performing any procedures on any pyrotechnic device, read all information contained within the Standard Workshop Practices section of this product. For additional information, refer to Standard Workshop Practices Standard Workshop Practices
The SRS features selective activation of the air bags and pretensioners, and two stage driver and passenger air bags. The RCM (restraints control module) monitors internal and external sensors and activates the required safety belt pretensioners and air bags if the sensors detect an impact or roll-over above preset limits.
DRIVER AIR BAG
The driver air bag forms the center pad of the steering wheel. Four pins and two latches locate and secure the driver air bag to the steering wheel. The latches consist of wire springs on each side of the driver air bag which engage with hooks in the steering wheel. The driver air bag is released from the steering wheel by pulling on the wire springs with a special tool inserted through a slot on each side of the steering wheel hub. Springs on the locating pins then push the driver air bag away from the steering wheel.
A Lucar connector attaches a ground to the driver air bag.
The driver air bag has a two stage inflator, with separate electrical connectors for each stage. The inflator contains a non-azide propellant as the gas generator.
Lines moulded into the inner surface of the driver air bag cover provide weak points that split open in a controlled manner when the driver air bag deploys. The inflated volume of the air bag is 57 liters (2.01 ft3).
PASSENGER AIR BAG
The passenger air bag is located in the instrument panel, behind the upper glove compartment. The bottom of the passenger air bag is attached to a mounting bracket on the in-vehicle crossbeam. The top of the passenger air bag is attached to a chute, which, in turn, is attached to a reinforcement lid in the top of the instrument panel. When the air bag deploys, the chute guides the air bag to the underside of the reinforcement lid. The reinforcement lid incorporates two deployment doors that are forced open, splitting the instrument panel covering, when the air bag deploys.
A Lucar connector attaches a ground to the passenger air bag.
The passenger air bag has a two stage inflator, with separate electrical connectors for each stage. The inflator contains a non-azide propellant as the gas generator. The inflator uses a high pressure mix of air and hydrogen gas as the inflation medium. The inflated volume of the air bag is 130 liters (4.59 ft3).
SIDE AIR BAGS
NOTE:
Left side air bag shown, right side air bag is mirror image
A side air bag is attached to the outside of each front seat backrest frame, under the backrest cover.
The side air bags are handed, and each consist of a moulded plastic case which contains the folded air bag and the inflator. A cable connects the igniter of the inflator to a connector in the main seat harness connector block located under the front edge of the seat cushion.
When the air bag deploys it forces the front edge of the moulded plastic case apart and splits open the backrest cover.
The side air bags use compressed argon as the inflation medium. The inflated volume of each side air bag is 12 liters (0.42 ft3).
SIDE AIR CURTAINS
The side air curtains are designed to protect the head and upper body in side impact and roll-over situations. The first and second row side air curtains are a standard fit on all vehicles. The third row side air curtains are fitted on seven seat vehicles only. The side air curtains use compressed argon as the inflation medium.
First and Second Row Side Air Curtain
NOTE:
Right side air curtain shown, left side air curtain is mirror image
The first and second row side air curtains are installed on the cant rails above the front and rear doors, behind the headliner.
Each side air curtain has an inflator, which is attached to the header rail by a mounting bracket and two screws. The inflator is connected to the air curtain by a gas guide pipe.
The gas guide pipe and air curtain are secured along the cant rail by a fixing at the front of the gas guide pipe, two fixings at the B pillar ramp, two clips and two screws, and two fixings at the end of the gas guide pipe and C pillar ramp.
At the rear of the air curtain, an active tether device is clipped in two positions down the C pillar. At the bottom of the active tether device is a fixing anchorage.
The front of the air curtain is secured to the A pillar by two fixings.
When the side air curtain deploys, it breaks out of the B pillar ramp and the clips on the cant rail and extends downwards from behind the headliner. The deploying air curtain is tensioned between the anchorage points on the A pillar and the active tether device on the C pillar. This retains the air curtain in position against the upper part of the doors and the B pillar.
Third Row Side Air Curtain
NOTE:
Right side air curtain shown, left side air curtain is mirror image
The third row side air curtains are installed on the cant rails above the rear quarter windows, behind the headliner.
Each side air curtain has an inflator, which is attached to the D pillar by a mounting bracket and two screws. The inflator is connected to the air curtain by a gas guide pipe. The gas guide pipe and air curtain are secured to the cant rail by two screws. Tethers are attached to the front and rear of the air curtain. The front tether is anchored to the C pillar. The rear tether is anchored to the D pillar and held in position by a tether housing.
When a third row side air curtain deploys, it extends downwards from behind the headliner. The expanding air curtain tightens the tethers, which retain the air curtain in position against the rear quarter window.
PRETENSIONERS
The pretensioners are used to tighten the front safety belts during a collision to ensure the occupants are securely held in their seats. A pretensioner is integrated into each front safety belt buckle.
Each pretensioner has a tube containing an inflator and a piston. The inflator is connected to the RCM (restraints control module). The piston is attached to a steel cable, the opposite end of which is attached to the safety belt buckle.
On receipt of a fire signal from the RCM (restraints control module), the inflator generates nitrogen gas that rapidly expands to drive the piston along the tube, pulling the cable and drawing the safety belt buckle downwards.
SAFETY BELT SENSORS
The buckle of each front safety belt incorporates a Hall effect sensor that provides a safety belt status signal to the RCM (restraints control module). The RCM (restraints control module) broadcasts the status of the two front safety belts on the high speed CAN (controller area network) bus for use by the instrument cluster.
IMPACT SENSORS
Impact sensors are installed in the front and both sides of the vehicle. The use of multiple impact sensors provides shorter air bag trigger times, through faster detection of lateral and longitudinal acceleration, and improves detection accuracy.
There are two front impact sensors attached to brackets on the body front support frame, just above each front longitudinal.
There are six side impact sensors located in the passenger compartment, as follows:
- One attached to each front door.
- One attached to the base of each B pillar.
- One installed in each rear quarter, above the rear wheelarch.
Each impact sensor incorporates an accelerometer and a microcontroller powered by a feed from the RCM (restraints control module). The power feed also provides the interface connection through which the impact sensor communicates with the RCM (restraints control module) using serial data messages. Acceleration is evaluated by the microcontroller and transmitted to the RCM (restraints control module), which then makes the decision on whether or not to activate the air bags and pretensioners.
When the ignition is switched on the RCM (restraints control module) supplies power to the impact sensors, which perform a self test. After satisfactory self tests the impact sensors continually output 'sensor active' messages to the RCM (restraints control module). If a fault is detected the relevant impact sensor sends a fault message, instead of the sensor active message, to the RCM (restraints control module). The RCM (restraints control module) then stores a related fault code and illuminates the SRS (supplemental restraint system) warning indicator.
PASSENGER AIR
BAG DEACTIVATION INDICATOR
The passenger air bag deactivation indicator is installed on the center switch pack of the instrument panel. When appropriate, the indicator illuminates to advise front seat occupants that the passenger air bag is disabled. Operation of the indicator is controlled by the RCM (restraints control module) based on seat occupancy status derived from the occupant classification system (NAS vehicles) or the passenger air bag deactivation switch (all except NAS and Australian specification vehicles).
The RCM (restraints control module) illuminates the indicator when:
- The passenger air bag is deactivated with the passenger air bag deactivation switch (where fitted). OR
- Required by passenger seat occupant monitoring (NAS vehicles only).
PASSENGER AIR BAG DEACTIVATION SWITCH
The passenger air bag deactivation switch provides a method of manually disabling the passenger air bag on all vehicles except Australian specification and those fitted with the occupant classification system. The switch is installed in the front passenger end of the instrument panel and is operated by the ignition key.
When the passenger air bag deactivation switch is operated, it changes a ground connection between two pins in the connectors of the RCM (restraints control module). When the passenger air bag deactivation switch is selected to OFF, the RCM (restraints control module) disables the passenger air bag and, if the front passenger seat is occupied, illuminates the passenger air bag deactivation indicator.
OCCUPANT SENSING
There are 2 types of occupant sensing:
- In all markets except North America, vehicles have an occupant detection system to activate the seat belt minder
- On NAS vehicles, an occupant classification system provides signals to the RCM (restraints control module) to allow the correct arming of the passenger air bag and corresponding indicator.