Part 3
PASSENGER AIRBAGThe rearward facing surface of the passenger airbag door above the glove box is the most visible part of the passenger airbag. The airbag used in this model is a Next Generation-type that complies with revised federal airbag standards to deploy with less force than those used in some prior models. The passenger airbag is located in the instrument panel in front of the front seat passenger seating position, where it is secured to the instrument panel. Concealed beneath the passenger airbag door are the folded airbag cushion, the airbag retainer or housing, and the airbag inflator. The airbag inflator is a hybrid-type unit that is secured to and sealed within the airbag housing along with the folded airbag cushion. The airbag housing is constructed of a long U-shaped aluminum extrusion with two stamped steel end plates. 'Two tabs that extend from the bottom of the extrusion serve as the rear mounting brackets, while an angled foot on the bottom of each end plate serve as the front mounting brackets. The front brackets are secured with screws to the instrument panel armature above the glove box, while the rear brackets are secured with screws to the upper glove box opening reinforcement. A yellow connector on the end of a short, two-wire pigtail harness connects the passenger airbag inflator to the vehicle electrical system.
The molded plastic passenger airbag door has a predetermined horizontal breakout line near its center which is concealed beneath its decorative outer surface. Return flanges near the top and bottom of the airbag door feature windows that are engaged on hook formations at the top and bottom of the airbag housing. Three tabs extend downward from the lower return flange and are secured with the same screws that secure the glove box module to the upper glove box opening reinforcement. Five molded snap features along the top of the airbag door above the upper return flange snap into receptacles located in the instrument panel base trim just below the instrument panel top cover. Following a passenger airbag deployment, the passenger airbag and airbag door unit must be replaced. The passenger airbag cannot be repaired, and must be replaced if faulty or in any way damaged. The passenger airbag door is serviced only as a unit with the passenger airbag.
The passenger airbag is deployed by an electrical signal generated by the Airbag Control Module (ACM) through the passenger airbag line 1 and line 2 (or squib) circuits. The hybrid-type inflator assembly includes a small canister of highly compressed argon gas. When the ACM sends the proper electrical signal to the airbag inflator, the electrical energy generates enough heat to ignite chemical pellets within the inflator. Once ignited, these chemical pellets burn rapidly and produce the pressure necessary to rupture a containment disk in the argon gas canister. The inflator and argon gas canister are sealed to the airbag cushion so that all of the released argon gas is directed into the airbag cushion, causing the cushion to inflate. As the cushion inflates, the passenger airbag door will split at the breakout line and the two halves of the door will pivot out of the way. Following an airbag deployment, the airbag cushion quickly deflates by venting the argon gas through vents on the instrument panel side of the airbag cushion.
Some of the chemicals used to create the pressure to burst the argon gas containment disk are considered hazardous in their solid state, before they are burned, but they are securely sealed within the airbag inflator. However, the gas that is produced when the chemicals are burned is harmless. A small amount of residue from the burned chemicals may cause some temporary discomfort if it contacts the skin, eyes, or breathing passages. If skin or eye irritation is noticed, rinse the affected area with plenty of cool, clean water. If breathing passages are irritated, move to another area where there is plenty of clean, fresh air to breath. If the irritation is not alleviated by these actions, contact a physician immediately.
SEAT BELT SWITCH
The seat belt switch is a small, normally open, single pole, single throw, plunger actuated, momentary switch. Only one seat belt switch is installed in the vehicle, and it is integral to the driver seat belt retractor assembly. The seat belt switch is connected to the vehicle electrical system through a short pigtail wire to a dedicated take out and connector of the body wire harness.
The seat belt switch cannot be adjusted or repaired and, if faulty or damaged, the entire driver seat belt and retractor unit must be replaced.
The seat belt switch is designed to control a path to ground for the seat belt switch sense input of the Electro-Mechanical Instrument Cluster (EMIC). The seat belt switch plunger is actuated by the seat belt webbing wound onto the seat belt retractor spool. When the seat belt tip-half webbing is pulled out of the retractor far enough to engage the seat belt buckle-half, the switch plunger is extended and closes the seat belt switch sense circuit to ground; and, when the seat belt tip-half webbing is wound onto the retractor the switch plunger is depressed, opening the ground path. The EMIC monitors the seat belt switch status, then controls the seatbelt indicator and sends electronic chime request messages over the Programmable Communications Interface (PCI) data bus to the Central Timer Module (CTM) based upon that input.
The seat belt switch receives ground through its pigtail wire connection to the body wire harness from another take out of the body wire harness. An eyelet terminal connector on that ground take out is secured under a ground screw to the left lower B-pillar. The seat belt switch is connected in series between ground and the seat belt switch sense input of the EMIC.
SEAT BELT TENSIONER
Seat belt tensioners supplement the airbag system for this model. The seat belt tensioners are integral to the front seat belt retractors, which are secured within each B-pillar in the vehicle where they are concealed behind the B-pillar trim. The seat belt tensioner consists primarily of a sprocket/pinion, a steel tube, a cast metal housing, numerous steel balls, a stamped metal ball trap, a torsion bar, a small pyrotechnically activated gas generator, and a short pigtail wire. All of these components are located on one side of the retractor spool on the outside of the retractor housing except for the torsion bar, which serves as the spindle upon which the retractor spool rides. The seat belt tensioners are controlled by the Airbag Control Module (ACM) and are connected to the vehicle electrical system through a dedicated take out of the body wire harness by a keyed and latching molded plastic connector insulator to ensure a secure connection.
The seat belt tensioners cannot be repaired and, if faulty or damaged, the entire front seat belt, retractor, and tensioner unit must be replaced. The seat belt tensioners are not intended for reuse, and both tensioners must be replaced following any airbag deployment. A growling or grinding sound while attempting to operate the seat belt retractor is a sure indication that the seat belt tensioner has been deployed and requires replacement. For seat belt tensioner service procedures, (Refer to FRONT SEAT BELT & RETRACTOR - REMOVAL).
The seat belt tensioners are deployed in conjunction with the airbags by a signal generated by the Airbag Control Module (ACM) through the driver or passenger seat belt tensioner line 1 and line 2 (or squib) circuits. When the ACM sends the proper electrical signal to the tensioner, the electrical energy generates enough heat to initiate a small pyrotechnic gas generator. The gas generator is installed in one end of a steel tube that contains numerous steel balls. As the gas expands, it pushes the steel balls through the tube into a cast metal housing, where a ball guide directs the balls into engagement with the teeth of a sprocket that is geared to one end of the retractor spool. As the balls drive past the sprocket, the sprocket turns and drives the seat belt retractor spool causing the slack to be removed from the front seat belts. The ball trap captures the balls as they leave the sprocket and are expelled from the housing. Removing excess slack from the front seat belts not only keeps the occupants properly positioned for an airbag deployment following a frontal impact of the vehicle, but also helps to reduce the likelihood of a harmful contact with interior components. Also, the seat belt tensioner torsion bar that the retractor spool rides upon is designed to deform in order to control the loading being applied to the occupants by the seat belts during a frontal impact, further reducing the potential for occupant injuries.
The ACM monitors the condition of the seat belt tensioners through circuit resistance, and will illuminate the airbag indicator in the instrument cluster and store a Diagnostic Trouble Code (DTC) for any fault that is detected. For proper diagnosis of the seat belt tensioners, a DRB III scan tool is required. Refer to the appropriate diagnostic information.