Passive Restraints - Airbag System: Notes
The Passive Restraints are referred to as a supplemental restraint system because they were designed and are intended to enhance the protection for the occupants of the vehicle ONLY when used in conjunction with the seat belts or active restraints. They are referred to as passive restraints because the vehicle occupants are not required to do anything to make them operate; however, the vehicle occupants must be wearing their seat belts in order to obtain the maximum safety benefit from the supplemental restraint system.
The supplemental restraint system electrical circuits are continuously monitored and controlled by a microprocessor and software contained within the Occupant Restraint Controller (ORC). An airbag indicator in the Instrument Cluster illuminates for about seven seconds as a bulb test each time the ignition switch is turned to the ON or START positions. Following the bulb test, the airbag indicator is turned ON or OFF by the ORC to indicate the status of the supplemental restraint system. If the airbag indicator comes on at any time other than during the bulb test, it indicates that there is a problem in the supplemental restraint system electrical circuits. Such a problem may cause airbags not to deploy when required, or to deploy when not required.
Deployment of the supplemental restraints 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) upon the impact sensors. 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 front seat belt tensioners are provided with a deployment signal by the ORC in conjunction with the front airbags and driver knee blocker airbag. During a frontal vehicle impact, the knee blockers work in concert with properly fastened and adjusted seat belts to restrain both the driver and the front seat passenger in the proper position for an airbag deployment. The knee blockers also absorb and distribute the crash energy from the driver and the front seat passenger to the structure of the instrument panel. The seat belt tensioner removes the slack from the front seat belts to provide further assurance that the driver and front seat passenger are properly positioned and restrained for an airbag deployment.
When the ORC monitors a problem in any of the airbag system circuits or components, including the seat belt tensioners, it stores a fault code or Diagnostic Trouble Code (DTC) in its memory circuit and sends an electronic message to the cluster to turn on the airbag indicator. Proper testing of the airbag system components, the Programmable Communications Interface (PCI) data bus, the electronic message inputs to and outputs from the cluster or the ORC, as well as the retrieval or erasure of a DTC from the ORC or cluster requires the use of a scan tool. Refer to BODY DIAGNOSTIC PROCEDURES article .
The ORC determines if an impact is severe enough to require the airbags to inflate. Based on the level of collision severity, the ORC determines the proper rate of inflation. The front airbag inflators are designed to provide different rates of airbag inflation. The ORC will not detect roll over collisions.
The ORC also monitors the readiness of the electronic parts of the system whenever the ignition switch is in the START or ON positions. If the key is in the OFF position, in the ACC position, or not in the ignition switch, the front airbags are not on and will not inflate.
The ORC sends a message to the cluster to turn on the AIRBAG light in the instrument panel for 6 to 8 seconds when the ignition switch is first turned ON, then turns the light OFF. If the ORC detects a malfunction in any part of the system, the airbag light will turn ON either momentarily or continuously.
When the ORC detects a collision requiring the Front Airbags , it signals the inflator units. A large quantity of nontoxic gas is generated to inflate the front airbags. Different front airbag inflation rates are possible, these rates are determined by the ORC based on collision severity. The front airbag covers separate and fold out of the way as the front airbags inflate to their full size. The front airbags fully inflate in about 50 milliseconds. This is only about half of the time it takes you to blink your eyes. The front airbags then quickly deflate while helping to restrain the driver and front passenger. The driver's and passenger's front airbag gas is vented through the airbag material and small vent openings towards the instrument panel. In this way the front airbags do not interfere with your control of the vehicle.
The Supplemental Curtain Airbags are designed to activate only in certain side collisions. When the ORC detects a collision requiring the curtain airbags to inflate, it signals the inflators on the crash side of the vehicle. A quantity of nontoxic gas is generated to inflate the curtain airbag. The inflating curtain airbag pushes the outside edge of the headliner out of the way and inflates (in about the same time it takes to blink your eyes). A properly belted and seated occupant is less likely to be injured by the force of the airbag or crash event. Items that are positioned in the area where the curtain airbag inflates can reduce the effectiveness of the airbag and also increase the likelihood of injuries to the occupants, this especially applies to children. The curtain airbag is about 4 inches (10 cm) thick when it is inflated.
When the ORC detects a collision requiring the Knee Blocker Airbag , it signals the inflator unit. A quantity of nontoxic gas is generated to inflate the Knee Blocker Airbag. The Knee Blocker Airbag inflates rearward towards the driver's knees to help protect the knees and position the driver for the best interaction with the front airbag. The Knee Blocker Airbag fully inflates in about 50 milliseconds, this is only about half of the time it takes you to blink your eyes. It then quickly deflates while helping to protect the driver's knees.
Knee Impact Blockers - Help protect the knees and position you for the best interaction with the front airbags.
Enhanced Accident Response - If the airbags and seat belt tensioners deploy after an impact and the electrical system remains functional, vehicles equipped with power door locks will unlock automatically. In addition, approximately 5 seconds after the vehicle has stopped moving, the interior lights will illuminate until the ignition switch is turned off.