Air Bag, Knee Blocker: Operation

The Knee AirBag (KAB) is deployed by an electrical signal generated by the Occupant Restraint Controller (ORC) to which it is connected through a KAB line 1 (or squib) circuit to the initiator in the airbag inflator. When the ORC sends the proper electrical signals to the 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 KAB deployment door will split at predetermined tear seam lines concealed on the underside of the door, then the door will fold open and out of the way. The cushion protects the lower extremities of the vehicle operator and helps to keep the seat occupant properly positioned for the Driver AirBag (DAB) deployment during a frontal impact collision. Following an airbag deployment, the KAB cushion quickly deflates by venting the inert gas through the loose weave of the fabric used to construct the instrument panel side of the airbag cushion, and the deflated cushion hangs down loosely from the lower instrument panel.

The ORC monitors the condition of the knee 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 KAB inflator and 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.