Part 2 Of 2
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 re-enforcement lid in the top of the instrument panel. The reinforcement lid incorporates a single door that opens, splitting the instrument panel covering, when the air bag deploys.
The passenger air bag is grounded through an earth track and the module's connection to the in-vehicle crossbeam.
The 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 in each stage. The inflated volume of the air bag is 121 liters (4.27 ft3).
SIDE AIR BAG
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 molded 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 molded 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).
FRONT HEAD AIR BAG
The front head air bags are installed behind the A pillar trim and above the outer edges of the headlining. The inflatable bag incorporates tether straps at each end which are attached to the body. When the air bag deploys, the inflating bag shortens in length and pulls on the tether straps, which forces it from behind the trim to cover the window in a straight line between the tether strap anchor points.
REAR HEAD AIR BAG
The rear head air bags are installed behind the outer edges of the headlining above the D pillar. When the air bag deploys, the inflating bag forces itself from behind the trim to cover the upper part of the D pillar and adjacent areas of the rear door and quarter light.
KNEE AIRBAG
The inflatable knee bolster air bag is located behind the driver's knee bolster panel below the steering column. The flanges of the inflatable knee bolster air bag are attached to a re-enforcement lid in the driver knee bolster panel. The reenforcement lid incorporates two deployment doors that are forced open, splitting the instrument panel covering, when the air bag deploys.
An EPC connector attaches a ground to the inflatable knee bolster air bag.
The inflatable knee bolster air bag has a single stage inflator with one connector on the outboard end. The inflator contains a non-azide propellant as the gas generator. The inflated volume of the air bag is 19 liters (0.67 ft3).
AIR BAG WARNING INDICATOR
The air bag warning indicator consists of a red LED (light emitting diode) behind a SRS (supplemental restraint system) graphic in the instrument cluster.
Operation of the air bag warning indicator is controlled by a high speed CAN (controller area network) bus message from the RCM (restraints control module) to the instrument cluster. The RCM (restraints control module) sends the signal to illuminate the air bag warning indicator if a fault is detected, and for approximately 6 seconds during the bulb check at the beginning of each ignition cycle.
BATTERY DISCONNECT UNIT
The battery disconnect unit is attached to the positive terminal on the battery and allows the RCM (restraints control module) to disconnect the main starter cable during a crash.
The battery disconnect unit incorporates the positive terminal connector and heavy duty cables for the starter and for engine and passenger compartment power distribution. The starter cable connection is contained in a plastic housing next to the battery terminal. The end fitting of the starter cable is a tapered press fit in one end of a gas discharge tube. The other end of the gas discharge tube contains a gas generator and a squib connected to the RCM (restraints control module).
When the RCM (restraints control module) fires the squib, the gas from the gas generator forces the end fitting of the starter cable out of the gas discharge tube and breaks the connection with the starter motor. As the end fitting is pushed out of the gas discharge tube, spring tabs in the plastic housing engage with the rim of the end fitting to hold it clear of the gas discharge tube.
The fuel pump motor is shut off by the ECM (engine control module) after the ECM (engine control module) receives a crash signal from the RCM (restraints control module).
CLOCKSPRING
The clockspring is installed on the steering column to provide the electrical interface between the fixed wiring harness and the steering wheel. The clockspring provides connections for the driver air bag, horn and steering wheel switch packs.
A rotating link harness is encapsulated into a plastic cassette comprising outer and inner housings with integral connectors. Brackets on the outer housing accommodate the column stalk switches. A spring loaded locking lever attached to the outer housing automatically engages and disengages with the inner housing when the steering wheel is removed and installed. To prevent damage to the rotating link harness, both the steering and the clockspring must be centralized when removing and installing the steering wheel.
SRS (supplemental restraint system) OPERATION
In a collision, the sudden deceleration or acceleration is measured by the impact sensors and the accelerometers in the restraints control module. The restraints control module evaluates the readings to determine the impact point on the vehicle and whether the deceleration/acceleration readings exceed the limits for firing any of the air bags, pretensioners, and battery disconnect unit. During a collision, the restraints control module only fires the air bags and pretensioners if the safing function confirms that the data from the impact sensor(s) indicates an impact limit has been exceeded.
The restraints control module incorporates the following impact thresholds to cater for different accident scenarios:
^ Front impact, pretensioners
^ Front impact, driver and passenger air bags stage 1, belt unfastened
^ Front impact, driver and passenger air bags stage 1, belt fastened
^ Front impact, driver and passenger air bags stage 2, belt unfastened
^ Front impact, driver and passenger air bags stage 2, belt fastened
^ Rear impact
^ Driver side impact
^ Passenger side impact.
The front impact thresholds increase in severity from pretensioners, through to driver and passenger air bag stage 2, belt fastened.
Firing Strategies
The safety belt pretensioners are fired when the pretensioner impact limit is exceeded. The restraints control module only fires the pretensioners if the related safety belt is fastened.
The driver and passenger air bags are only fired in a frontal impact. If an impact exceeds a stage 1 limit, but is less than the corresponding stage 2 limit, only one inflator in each air bag is fired (stage 2 is still fired for disposal after a delay of 100ms). If an impact exceeds the stage 2 limit, the two inflators in each air bag are fired simultaneously.
The passenger air bag is disabled unless the front passenger seat is occupied by a large person (NAS only), or the passenger air bag deactivation switch is on (all except NAS & AUS).
The stage 2 inflator of the driver air bag is disabled if the driver seat is forward of the switching point of the seat position sensor.
If there is a fault with a safety belt buckle sensor, the restraints control module assumes the related safety belt is fastened for the pretensioner firing strategy and unfastened for the driver and passenger air bag firing strategies. If there is a fault with the occupant classification sensor, the restraints control module disables the passenger air bag. If there is a fault with the passenger air bag deactivation switch, the restraints control module disables the passenger air bag.
If a side impact limit is exceeded, the restraints control module fires the side air bag and the side head air bag on that side of the vehicle. If the side impact limit on the front passenger side of the vehicle is exceeded, the restraints control module also evaluates the input from the occupant classification sensor, and fires the side air bag only if the front passenger seat is occupied by a large person (NAS only).
If multiple impacts occur during a crash event, after responding to the primary impact the restraints control module will output the appropriate fire signals in response to any further impacts if unfired units are available.
The battery disconnect unit is fired:
^ At driver and passenger air bag belt fastened threshold in a frontal impact
^ At the driver and passenger side impact threshold in a side impact
^ At the rear impact threshold in a rear impact.
Crash Signal
When the RCM (restraints control module) outputs any of the fire signals it also outputs a crash signal to the GEM (generic electronic module) and the ECM (engine control module) on the High speed CAN (controller area network). The crash signal is also hardwired to the ECM (engine control module) and the GEM (generic electronic module). The instrument cluster picks up the crash signal from the High speed CAN (controller area network) and gateways it to the LCM (lighting control module). On receipt of the crash signal, the GEM (generic electronic module) goes into a crash mode and the ECM (engine control module) cuts the power supply to the fuel pump relay. In the crash mode, the GEM (generic electronic module):
^ Activates all of the unlock signals of the vehicle locking system, even if the vehicle is already unlocked.
^ Ignores all locking/superlocking inputs until it receives an unlock input, when it returns the locking system to normal operation.
^ Activates the interior lamps. The interior lamps remain on permanently until they are manually switched off at the lamp unit, or the GEM (generic electronic module) crash mode is switched off and they return to normal operation.
^ Disables the rear window child lock input until the crash mode is switched off.
^ Sends a crash message to the LCM (lighting control module), via the K bus, to activate the hazard flashers. The hazard flashers remain on until cancelled by the hazard warning switch or the crash mode is switched off.
The GEM (generic electronic module) crash mode is switched off by a valid locking and unlocking cycle of the locking system.
CONTROL DIAGRAM SHEET 1 OF 2
NOTE: A = Hardwired; D = High Speed CAN
CONTROL DIAGRAM SHEET 2 OF 2
NOTE: A = Hardwired; D = High speed CAN (controller area network) bus
