Air Bag, Passenger: Operation
The multistage Passenger AirBag (PAB) and active vent (domestic market vehicles only) is deployed by electrical signals generated by the Occupant Restraint Controller (ORC) through PAB squib 1 and squib 2 circuits to the two initiators in the airbag inflator, and by a PAB squib 3 circuit to the initiator of the Micro Gas Generator (MGG) for the active vent. By using two initiators and an active vent, the PAB can be deployed at multiple levels of force. The force level is managed by the ORC to suit the monitored impact conditions by providing one of multiple delay intervals between the electrical signals provided to the two initiators and the tether release. The longer the delay between the initiator signals and the sooner the active vent is opened, the less forcefully the PAB will deploy.
When the ORC sends the proper electrical signals to each initiator, the electrical energy generates enough heat to initiate a small pyrotechnic charge which, in turn ignites chemical pellets within the inflator. Once ignited, these chemical pellets burn rapidly and produce a large quantity of inert gas. The inflator is sealed to the airbag cushion and a diffuser in the inflator directs all of the inert gas into the airbag cushion, causing the cushion to inflate. As the cushion inflates, the PAB door will split at predetermined tear seam lines concealed on the inside surface of the door, then the door will pivot up over the top of the instrument panel and out of the way. Following an airbag deployment, the airbag cushion quickly deflates by venting the inert gas through a discrete vent in each fabric side panel of the airbag cushion.
The MGG inflates a small cushion within the primary cushion to control the active vent. The ORC monitors a seat track position sensor on the passenger front seat. If the seat is in the full forward position when an airbag deployment occurs, the ORC keeps the active vent open. With the active vent open the airbag deployment is less forceful, which reduces the possibility of an airbag-induced injury when the passenger is seated close to the deploying airbag. If the passenger front seat is not in the full forward position, the active vent is closed during airbag deployment.
Typically, all initiators are used during a PAB deployment event. However, it is possible for only one initiator to be used during a deployment due to an airbag system fault; therefore, it is necessary to always confirm that all initiators have been used in order to avoid the improper disposal of potentially live pyrotechnic materials. Refer to HANDLING NON-DEPLOYED SUPPLEMENTAL RESTRAINTS .
The ORC monitors the condition of the passenger airbag through circuit resistance. If any fault is detected the ORC will illuminate the airbag indicator in the instrument cluster and store a Diagnostic Trouble Code (DTC). Proper diagnosis of the PAB inflator, the active vent MGG and the squib circuits requires the use of a diagnostic scan tool and may also require the use of the Airbag Kit. Refer to the appropriate diagnostic information.