Restraints and Safety Systems: Description and Operation
Occupant restraints for this vehicle include both Active and Passive
types. Active restraints are those which require the occupants to take some action to employ, such as fastening the seat belt; while Passive restraints require no action by the occupants to be employed.
ACTIVE RESTRAINTS
The Active restraints include:
Front Driver and Passenger Seat Belts - Both seating positions are equipped with a three-point restraint. Seat Belt Tensioners (SBT) that actuate to remove slack in the seat belts and to snug the occupant into the seat at the onset of an impact event. This controls the occupant's forward movement to reduce the likelihood of injury as a result of contacting any interior components. Especially during the primary impact event phase, the tensioning power of the SBTs guarantees optimum transmission of the passenger compartment deceleration to the passenger. The vehicle's SBTs employ load-limiting retractors that "give" with higher seat belt loads. If a given seat belt force is exceeded, the seat belt force limiter permits a controlled forward inclination of the occupant's upper body. This protective function reduces the risk of chest and shoulder injuries and permits the passenger to plunge deeper into the airbag for a smooth dissipation of the occupant's kinetic energy. The drivers SBT is mounted in the B pillar below the belt line which locks only as a result of a sudden vehicle stop or a rapid extension of the webbing. This is called "Emergency Locking", it will allow free movement under normal driving conditions. To allow the retention of a child seat, a dual-mode passenger SBT is mounted in the B pillar below the belt line and can be switched between "Emergency Locking" and "Automatic Locking". Seat-mounted, inboard buckles allow seat adjustment while maintaining a consistent relationship between the buckle and the seat belt. For easy and consistent access and adjustment, a free-running latch plate on each belt slides along the webbing and stops against a button near the occupant's shoulder when unfastened. A seat belt warning lamp in the Instrument Cluster (IC) comes on and a warning chime sounds for a short time if the driver's seat belt is not fastened when the ignition switch is turned to the "RUN" position. After starting the engine, the seat belt warning indicator flashes briefly as an added precaution.
Child Restraint Anchors - The front passenger seat includes a LATCH (Lower Anchors and Tether for Children) child seat anchorage system. LATCH-compatible child seats are those engineered for retention by direct attachment to the vehicle's seat structure rather than with the vehicle's seat belts. The child seat's lower anchors attach to the seat structure via heavy-gauge wire loops at the intersection of the seat cushion and seat back. The child seat's upper tether strap attaches to a child seat tether anchor. Child seats can also be securely fastened in the passenger seat using the seat belts. For this purpose, the passenger seat belt includes a dual-mode SBT. After the child seat is positioned and the belt routed according to instructions for the child seat, the seat belt is pulled all the way out of the SBT to the end of its travel. This switches the SBT to the "Automatic Locking" mode. As the seat belt retracts, the SBT locks to prevent the belt from being pulled out again. Pulling the belt snugly over the child seat secures the seat in place. When the belt retracts fully after child seat removal, normal "Emergency Locking" action is restored to the SBT.
PASSIVE RESTRAINTS
The passive restraints include:
Driver and Passenger Front Airbags - This airbag system is a passive, inflatable, Supplemental Restraint System (SRS). Vehicles with this equipment can be readily identified by the "SRS AIRBAG" logo molded into the driver airbag trim cover in the steering wheel (1) and also into the passenger airbag area (2) of the instrument panel top pad above the glove box.
Vehicles with the SRS can also be identified by the Airbag Warning Indicator, which will illuminate in the Instrument Cluster (IC) for about six seconds as a bulb test each time the ignition switch is turned to the "RUN" position.
The Supplemental Restraint System (SRS) also includes the following major components.
Occupant Restraint Controller (ORC) - The Occupant Restraint Controller (ORC) is located on a mount on the floor panel transmission tunnel (2) in front of the shifter, under the front center console.
ORC System Logic - The Supplemental Restraint System (SRS) uses an impact severity level (threshold) to determine the appropriate response from the ORC. Impacts that exceed the initial threshold in frontal, front-angled and rear impacts trigger only the SBTs, only if the seat belts are fastened, but trigger the airbags if the seat belts are not fastened. Impacts that exceed the higher threshold always trigger the airbags. The driver and passenger SRS systems operate independently of one another based on seat belt use. SET actuation occurs only if the seat belts are buckled. After an impact that activates an SET, the SET assembly must be replaced. The ORC monitors operational readiness of SRS and illuminates the airbag warning indicator lamp in the Instrument Cluster (IC) if a malfunction should occur. The following system components are monitored or undergo a self-check at startup. The side-impact sensor, airbag ignition circuits (squibs), seat belt buckle switches and the SET. The airbag warning indicator lamp also illuminates briefly each time the engine is started, allowing the driver to verify its operation.
Airbag Warning Indicator Lamp - The airbag warning indicator lamp is integral to the Instrument Cluster (IC), which is located on the Instrument Panel (IP) in front of the driver.
Clockspring - The clockspring is located at the top of the steering column, directly beneath the steering wheel where it is attached to the column by two screws (1).
Driver Front Airbag - The driver front airbag (1) is located in the center of the steering wheel, as part of the steering wheel trim cover.
Passenger Front Airbag - The passenger front airbag (1) is located on the instrument panel structural duct, beneath the instrument panel top pad and above the glove box.
The passenger front air bag can be deactivated when a child seat or small child occupies that seat by using the ignition key to turn the switch (1) to the OFF position. This will illuminate the passenger airbag OFF warning lamp on the center console. This indicates that the passenger front airbag is deactivated. The passenger front airbag will not be activated until the switch is turned to ON position and the passenger airbag OFF warning lamp goes out.
The passenger airbag off warning lamp (1) in the center console illuminates when the air bag is deactivated.
Side Impact Sensor - Two side impact sensors (2) are installed, one left side and one right side. One sensor is located under the carpet directly below each of the front seats.
Side Impact Airbag - The side impact airbags are concealed behind the door trim panels above the armrest. The side impact airbag is riveted (1) to the door's interior structure and activated by a squib (2). SRS logos on the trim panels denote the presence of the airbags. If the airbag is triggered during a lateral collision, the airbag tears open a seam on the inner door trim and inflates within 0.007 seconds to form a protective cushion between the passenger and the door. Thus the impact on the passenger's thorax and the ejecting motion of the head, which might otherwise cause serious injuries, are reduced.
The ORC and the Instrument Cluster (IC) each contain a central processing unit and programming that allow them to communicate with each other using the Controller Area Network (CAN). This method of communication is used by the ORC for control of the airbag indicator lamp.
Hard wired circuitry connects the SRS components to each other through the electrical system of the vehicle. These hard wired circuits are integral to several wire harnesses, which are routed throughout the vehicle and retained by many different methods. These circuits may be connected to each other, to the vehicle electrical system, and to the SRS components through the use of a combination of soldered splices, splice block connectors, and many different types of wire harness terminal connectors and insulators. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, further details on wire harness routing and retention, as well as pin-out and location views for the various wire harness connectors, splices and grounds.
ACTIVE RESTRAINTS
The primary passenger restraints in this or any other vehicle are the standard equipment factory-installed seat belts and child restraint anchors. Seat belts and child restraint anchors are referred to as an active restraint because the occupants are required to physically fasten and properly adjust these restraints in order to benefit from them. See the Owner's Manual in the vehicle glove box for more information on the features, use, and operation of all of the factory-installed active restraints.
PASSIVE RESTRAINTS
The driver/passenger airbags and the driver/passenger Seat Belt Tensioners (SET) were designed to reduce the risk of an injury to the chest and head in the event of a head-on collision.
The side airbags were designed to protect primarily the upper body and also to help protect the head in the event of a side collision.
Malfunctions in the SRS system are indicated on the Instrument Cluster (IC) by the airbag warning indicator lamp.
SRS -AIRBAG WARNING INDICATOR
The SRS airbag warning indicator lamp indicates that the SRS is ready for operation. When no faults are present in the system, the airbag warning indicator illuminates when the ignition switch is turned to the ON or RUN position and then goes out after approximately six seconds.
An error or malfunction is indicated in the SRS by the airbag warning indicator not illuminating when the ignition switch is turned to the ON or RUN position or not going out after six seconds.
Errors and malfunctions not endangering occupant protection are indicated by the airbag warning indicator illuminating for approximately two minutes when the ignition switch is turned to the ON or RUN position.
Errors and malfunctions which may endanger the occupant are indicated by the airbag warning indicator illuminating continuously.
In the case of an error or a malfunction the entire system should be checked according to the diagnosis instructions. The active restraints ARE NOT affected by an error or a malfunction in the SRS and remain operational.
PASSENGER AIRBAG OFF INDICATOR LAMP
The passenger Airbag Off Indicator Lamp operates in conjunction with the Passenger Airbag On/Off Switch. When the switch is turned to either the On or the Off position, the switch position is communicated to the Passenger Seat Occupant Simulator. The Passenger Seat Occupant Simulator then translates the switch position into a signal that the Occupant Restraint Controller is capable of reading in order to switch the Passenger Airbag on or off depending upon the Switch position. The Passenger Airbag Off Indicator Lamp will stay illuminated as long as the Passenger Airbag On/Off Switch is in the Off position.
FRONT END MEDIUM-SEVERE HEAD ON COLLISION SRS OPERATION
Only the seat belt tensioners (SET) are triggered The ORC registers medium-deceleration (stage-one threshold) due to a collision
The triggering pulse is transferred only to the SET squibs, because the restraint function of the seat belts in combination with the SET is sufficient enough to effectively protect the vehicles passengers for this type of collision
A check is made whether the seat belts are fastened If a seat belt is not fastened and the stage one threshold is exceeded the driver and passenger airbags are triggered to provide protection for the front passengers
FRONT END SEVERE HEAD-ON COLLISION SRS OPERATION
"Stage two threshold" The ORC recognizes the vehicles rapid deceleration due to a collision. The ORC routes the triggering pulse to the driver and passenger airbag squibs. At the same time the driver and passenger SBTs are also triggered.
REAR-END COLLISION SRS OPERATION
When the ORC registers sudden acceleration which exceeds the forward threshold value a check is made to determine which front seat belts are fastened. The ORC then activates only the SBTs which have fastened seat belts. The driver/passenger airbags are not activated unless a frontal collision which exceeds the stage two threshold is detected.
SIDE IMPACT COLLISION SRS OPERATION
When either the driver or passenger side impact side airbag sensor detects a sudden lateral acceleration which exceeds the lateral threshold value a signal is sent to the ORC. The ORC then deploys the appropriate side airbag.
The SRS electrical circuits are continuously monitored and controlled by a microprocessor and software contained within the Occupant Restraint Controller (ORC) (1). An airbag warning indicator lamp in the Instrument Cluster (IC) illuminates for about six seconds as a bulb test each time the ignition switch is turned to the On or Start positions. Following the bulb test, the airbag warning indicator lamp is turned On or Off by the ORC to indicate the status of the SRS. If the airbag warning indicator lamp comes on at any time other than during the bulb test, it indicates that there is a concern in the SRS electrical circuits. Such a problem may cause airbags to not deploy when required, or to deploy when not required.
Deployment of the driver and passenger airbags depends upon the angle and severity of an impact. Deployment is not based upon vehicle speed; rather, deployment is based upon the rate of deceleration as measured by the forces of gravity (G force). When an impact is severe enough, the microprocessor in the ORC signals the inflator of the appropriate airbag units to deploy their airbag cushions. The SET is provided with a deployment signal by the ORC in conjunction with the driver and passenger airbags. During a frontal vehicle impact, the seat belts are used to restrain both the driver and the passenger in the proper position for an airbag deployment. The SET removes the slack from the seat belts to provide further assurance that the driver and passenger are properly positioned and restrained for an airbag deployment.
Typically, the vehicle occupants recall more about the events preceding and following a collision than they do of an airbag deployment itself. This is because the airbag deployment and deflation occur so rapidly. In a typical 30 mile-per-hour (48 kilometer-per-hour) barrier impact, from the moment of impact until the airbags are fully inflated takes about 40 milliseconds. Within one to two seconds from the moment of impact, the airbags are almost entirely deflated. The times cited for these events are approximations, which apply only to a barrier impact at the given speed. Actual times will vary somewhat, depending upon the vehicle speed, impact angle, severity of the impact, and the type of collision.
When the ORC monitors a concern in any of the SRS circuits or components, including the SET, it stores a fault code or Diagnostic Trouble Code (DTC) in its memory circuit and sends an electronic message to the IC via the CAN to illuminate the airbag warning indicator. Proper testing of the SRS components, CAN data bus, ORC signals, and DTC information requires the use of a DRBIII(R) scan tool. Refer to the appropriate diagnostic information.
See the Owners Manual in the vehicle glove box for more information regarding features, use, and operation of all of the factory-installed active restraints.