DESCRIPTION
An occupant restraint system is standard factory-installed safety equipment on this vehicle. Available occupant restraints for this vehicle include both active and passive types. Active restraints are those which require the vehicle occupants to take some action to employ, such as fastening and adjusting a seat belt; while passive restraints require no action by the vehicle occupants to be employed.
OPERATION
The multistage driver airbag is deployed by electrical signals generated by the Occupant Restraint Controller (ORC) through the driver airbag squib 1 and squib 2 circuits to the two initiators in the airbag inflator. By using two initiators, the airbag can be deployed at multiple levels of force. The force level is controlled by the ORC to suit the monitored impact conditions by providing one of several delay intervals between the electrical signals provided to the two initiators. The longer the delay between these signals, the less forcefully the airbag 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 back of the airbag housing 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 driver airbag trim cover will split at predetermined breakout lines, then fold back out of the way. Following an airbag deployment, the airbag cushion quickly deflates by venting the inert gas towards the instrument panel through vent holes within the fabric used to construct the back (steering wheel side) panel of the airbag cushion.
Some of the chemicals used to create the inert gas may be considered hazardous while in their solid state before they are burned, but they are securely sealed within the airbag inflator. Typically, both initiators are used and all potentially hazardous chemicals are burned during an airbag 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 both initiators have been used in order to avoid the improper disposal of potentially live pyrotechnic or hazardous materials. Refer to Standard Procedure .
The inert gas that is produced when the chemicals are burned is harmless. However, 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 noted, 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.
Proper diagnosis of the driver airbag inflator and squib circuits requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.
The multistage passenger airbag is deployed by electrical signals generated by the Occupant Restraint Controller (ORC) through the passenger airbag squib 1 and squib 2 circuits to the two initiators in the airbag inflator. By using two initiators, the airbag can be deployed at multiple levels of force. The force level is controlled 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. The longer the delay between these signals, the less forcefully the airbag 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 passenger airbag door area of the instrument panel top pad will split at predetermined tear seam lines concealed on the underside of the instrument panel trim cover, 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 hole in each fabric side panel of the airbag cushion.
The airbag cushion in this vehicle also has an active vent located on each side of the cushion. The active vents close during an unobstructed deployment to provide a fully inflated bag. However, if the deployment is obstructed by an out-of-position passenger, the active vents open to reduce the likelihood of an airbag-induced injury.
Typically, both initiators are used during an airbag 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 both initiators have been used in order to avoid the improper disposal of potentially live pyrotechnic materials. Refer to Standard Procedure .
Proper diagnosis of the passenger airbag inflator and the passenger airbag squib circuits requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.
Each side curtain airbag is deployed individually by an electrical signal generated by the Occupant Restraint Controller (ORC) to which it is connected through left or right curtain airbag line 1 and line 2 (or squib) circuits. The hybrid-type inflator assembly for each airbag contains a small canister of highly compressed inert gas. When the ORC sends the proper electrical signal to the airbag inflator, the electrical energy creates enough heat to ignite chemical pellets within the inflator.
Once ignited, these chemicals burn rapidly and produce the pressure necessary to rupture a containment disk in the inert gas canister. The inflator and inert gas canister are sealed and connected to a tubular manifold so that all of the released gas is directed into the folded curtain airbag cushion, causing the cushion to inflate. As the airbag cushion inflates it will drop down from the roof rail between the edge of the headliner and the side glass/body pillars to form a curtain-like cushion to protect the vehicle occupants during a side impact collision.
The front tether keeps the front portion of the side airbag cushion taut to the side of the vehicle, thus ensuring that the bag will deploy in the proper position. Following the airbag deployment, the airbag cushion slowly deflates by venting the inert gas through the loose weave of the cushion fabric, and the deflated cushion hangs down loosely from the roof rail.
Proper diagnosis of the side curtain airbag inflator and the curtain airbag squib circuits requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.
All vehicles manufactured for sale in the United States and Canada are required to be equipped with a Lower Anchors and Tether for Children, or LATCH child restraint anchorage system. In standard cab models, the outboard front passenger seat has a single set of anchor provisions for installing a LATCH-compatible child seat. In quad or crew cab models, the second row seats have two sets of anchor provisions for installing a LATCH-compatible child seat. A single seat may be mounted in the center seating position, or one in each outboard seating position. In mega cab models, the second row seats have three sets of anchor provisions to accommodate the installation of a LATCH-compatible child seat in any one, or all three of the second row seating positions.
With LATCH, child seats are secured by direct attachment to the vehicle seat structure, rather than by the seat belts. With LATCH-compatible child seats, lower anchors attach to the seat structure through heavy-gauge wire loops located at the intersection between the seat cushion and the seat back surfaces.
In standard cab models, two upper tether anchors are integral to the upper cab back panel reinforcement, one each for the front passenger and front center seating positions to secure the top tether strap of child seats equipped with this feature. In quad or crew cab models, three upper tether anchor loops are secured to the upper cab back panel reinforcement to secure the top tether strap of child seats equipped with this feature. These upper tether anchors work with both LATCH-compatible and other child seats equipped with a top tether strap. In mega cab models, three upper tether anchors are integral to the upper cab back panel reinforcement, one for each of the three second row seating positions to secure the top tether strap of child seats equipped with this feature.
The owner's information packet in the vehicle glove box contains details and suggestions on the proper use of all of the factory-installed child restraint anchors.
The clockspring is a mechanical electrical circuit component that is used to provide continuous electrical continuity between the fixed instrument panel wire harness and the electrical components mounted on or in the rotating steering wheel. On this vehicle the rotating electrical components include the driver airbag, the horn switch, the Electronic Vehicle Information Center (EVIC) switches, the speed control switches, the remote radio switches and the steering wheel heating element, if the vehicle is so equipped. The clockspring case is positioned and secured to the top of the steering column. The fixed connector receptacles on the back of the fixed clockspring case connect the clockspring to the vehicle electrical system through several take outs with connectors from the instrument panel wire harness.
The turn signal cancel cam is integral to the rim of the clockspring rotor hub within the clockspring case so it also moves with the rotation of the steering wheel. Two short, black-sleeved pigtail wires on the upper surface of the clockspring rotor connect the clockspring to the driver airbag, while a steering wheel wire harness connected to the connector receptacle on the upper surface of the clockspring rotor completes circuits to the horn switch, the speed control switch and, if the vehicle is so equipped, to the optional remote radio switches and EVIC switches on the steering wheel. A third pigtail wire is dedicated to providing the high current requirements of the heating element for the optional heated steering wheel received through a dedicated connection on the back of the clockspring through a set of slip rings internal to the clockspring case. Another connector receptacle found on the Steering Angle Sensor (SAS) on the back of the clockspring is dedicated to the inputs and outputs of the SAS.
Like the clockspring in a timepiece, the clockspring tape has travel limits and can be damaged by being wound too tightly during full stop-to-stop steering wheel rotation. To prevent this from occurring, the clockspring is centered when it is installed on the steering column. Centering the clockspring indexes the clockspring tape and the SAS integral to the clockspring to the movable steering components so that the tape can operate within its designed travel limits and the SAS can accurately monitor and communicate steering wheel inputs. However, if the clockspring is removed from the steering column or if the steering shaft is disconnected from the steering gear, the clockspring spool and the SAS can change position relative to the movable steering components and relative to each other. The clockspring must be replaced if proper centering has been compromised or the tape may be damaged and Diagnostic Trouble Codes (DTC) or faults may be set within the SAS.
Service replacement clocksprings are shipped pre-centered and with a plastic locking pin installed. This locking pin should not be removed until the clockspring has been installed on the steering column. If the locking pin is removed before the clockspring is installed on a steering column, the clockspring must be replaced with a new unit. Proper clockspring installation must also be confirmed by viewing the SAS Menu Item, Data Display function using a diagnostic scan tool.
The hard wired clockspring circuits as well as the hard wired inputs and outputs of the SAS may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the SAS or the electronic controls or communication between other modules and devices that provide features of the Electronic Stability Program (ESP) or the Supplemental Restraint System (SRS). The most reliable, efficient, and accurate means to diagnose the SAS or the electronic controls and communication related to ESP or SRS operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.
The microprocessor in the Occupant Restraint Controller (ORC) contains the Supplemental Restraint System (SRS) logic circuits and controls all of the SRS components. The ORC uses On-Board Diagnostics (OBD) and can communicate with other electronic modules in the vehicle as well as with the diagnostic scan tool using the Controller Area Network (CAN) data bus. This method of communication is used for control of the airbag indicator in the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) and for SRS diagnosis and testing through the 16-way Data Link Connector (DLC) located on the driver side lower edge of the instrument panel.
The ORC microprocessor continuously monitors all of the SRS electrical circuits to determine the system readiness. If the ORC detects a monitored system fault, it sets an active and stored Diagnostic Trouble Code (DTC) and sends electronic messages to the EMIC over the CAN data bus to turn ON the airbag indicator. An active fault only remains for the duration of the fault, or in some cases for the duration of the current ignition cycle, while a stored fault causes a DTC to be stored in memory by the ORC. For some DTCs, if a fault does not recur for a number of ignition cycles, the ORC will automatically erase the stored DTC. For other internal faults, the stored DTC is latched forever.
The ORC receives battery current through two circuits; a fused ignition switch output (run) circuit through a fuse in the Totally Integrated Power Module (TIPM), and a fused ignition switch output (run-start) circuit through a second fuse in the TIPM. The ORC receives ground through a ground circuit and take out of the instrument panel wire harness that is secured by a ground screw to the body sheet metal. These connections allow the ORC to be operational whenever the ignition switch is in the START or ON positions.
The ORC also contains an energy-storage capacitor. When the ignition switch is in the START or ON positions, this capacitor is continually being charged with enough electrical energy to deploy the SRS components for up to one second following a battery disconnect or failure. The purpose of the capacitor is to provide backup SRS protection in case there is a loss of battery current supply to the ORC during an impact.
Various sensors within the ORC are continuously monitored by the ORC logic. These internal sensors, along with several external impact sensor inputs allow the ORC to determine both the severity of an impact and to verify the necessity for deployment of any SRS components. Two remote front impact sensors are located on the back of the right and left ends of the lower radiator crossmember near the front of the vehicle. The electronic impact sensors are accelerometers that sense the rate of vehicle deceleration, which provides verification of the direction and severity of an impact.
The ORC also monitors inputs from an internal rollover sensor and up to six additional remote side impact sensors located within both the left and right front doors, B-pillars and C-pillars to control deployment of the side curtain airbag units.
The impact sensors within the ORC are electronic accelerometer sensors that provide an additional logic input to the ORC microprocessor. These sensors are used to verify the need for a SRS component deployment by detecting impact energy of a lesser magnitude than that of the primary electronic impact sensors, and must exceed a safing threshold in order for the SRS components to deploy. A separate impact sensor within the ORC provides confirmation to the ORC microprocessor of side impact forces. This separate sensor is a bi-directional unit that detects impact forces from either side of the vehicle.
Pre-programmed decision algorithms in the ORC microprocessor determine when the deceleration rate as signaled by the impact sensors indicate an impact that is severe enough to require SRS protection and, based upon the severity of the monitored impact, determines the level of front airbag deployment force required for each front seating position. When the programmed conditions are met, the ORC sends the proper electrical signals to deploy the dual multistage front airbags at the programmed force levels, the front seat belt tensioners and either side curtain airbag unit.
The hard wired inputs and outputs for the ORC may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the ORC or the electronic controls or communication between other modules and devices that provide features of the SRS. The most reliable, efficient, and accurate means to diagnose the ORC or the electronic controls and communication related to SRS operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.
The locked mode of the Automatic Locking Retractor (ALR) is engaged and the retractor is switched from operating as a standard inertia-type Emergency Locking Retractor (ELR) by first buckling the combination lap and shoulder belt buckle. Then grasp the shoulder belt and pull all of the webbing out of the retractor. Once all of the belt webbing is extracted from the spool, the retractor will automatically become engaged in the pre-locked automatic locking mode and will make a light, audible clicking or ratcheting sound as the shoulder belt is allowed to retract to confirm that the automatic locking mode is now engaged. Once the automatic locking mode is engaged, the retractor will remain locked and the belt will remain tight around whatever it is restraining.
The retractor is returned to standard emergency locking (inertia) mode by unbuckling the combination lap and shoulder belt buckle and allowing the belt webbing to be almost fully retracted onto the retractor spool. The emergency locking mode is confirmed by the absence of the light, audible clicking or ratcheting sound as the belt webbing retracts. This mode will allow the belt to unwind from and wind onto the retractor spool freely unless and until a predetermined inertia load is sensed, or until the retractor is again switched to the automatic locking mode.
Remote or satellite impact sensors are located in various locations in the vehicle. These sensors are mounted remotely from the impact sensor that is internal to the Occupant Restraint Controller (ORC). Sensors at the front of the vehicle provide an additional logic input for use by the Occupant Restraint Controller (ORC) to control the front airbags and the seat belt pretensioners. Sensors on each side of the vehicle provide an additional logic input for use by the ORC to control the side curtain airbags and the seat belt pretensioners. Two types of sensors are used in this vehicle. They are the acceleration-type and the pressure-type, which are described in further detail in the following paragraphs.
Scheme 1
Each vehicle has at least four, but as many as six remote acceleration-type impact sensors (1). Two front sensors, one each for the left and right sides of the vehicle are secured with a screw to the back of the right or left end of the lower radiator cross member within the engine compartment. Two side sensors, one each for the left and right sides of the vehicle are secured with a screw near the base of the right or left inner B-pillar within the passenger compartment. Quad cab or crew cab and mega cab models have two additional side sensors, one each for the left and right sides of the vehicle, secured with a screw near the base of the right or left inner C-pillar within the passenger compartment.
The right and left front impact sensors are identical in construction and calibration. The right and left side impact sensors are also identical in construction and calibration. Although the front and side impact sensors are similar in appearance and construction, they are not interchangeable. The front sensors are designed to withstand the harsher operating environment found within the engine compartment.
Each sensor housing has an integral connector receptacle (4), an integral anti-rotation pin (3), and an integral mounting hole (2) with a metal sleeve to provide crush protection. A cavity in the center of the molded plastic impact sensor housing contains the electronic circuitry of the sensor which includes an electronic communication chip and an electronic acceleration sensor. Potting material fills the cavity to seal and protect the internal electronic circuitry and components. The front impact sensors are each connected to the vehicle electrical system through a dedicated take out and connector of the Front End Module (FEM) wire harness, while the side impact sensors are connected through dedicated take outs and connectors of the body wire harness.
The acceleration-type impact sensors cannot be repaired or adjusted and, if damaged or ineffective, they must be replaced.
Scheme 2
Two pressure-type front door side impact sensors (2) are used on all standard cab versions of this vehicle as well as on early-build editions of other cab styles, one each for the left and right sides of the vehicle. Pressure-type impact sensors are not used on late-build editions of the club, crew or mega cab versions. These sensors are mounted remotely from the impact sensor that is internal to the Occupant Restraint Controller (ORC). Each pressure-type sensor is secured with two screws and is sealed by a resilient gasket (1) to the front door module carrier on the inside of each front door. The sensors are concealed behind the front door trim panel within the passenger compartment.
The right and left front door side impact sensors are identical in construction and calibration, and are interchangeable. The sensor housing has an integral connector receptacle (3), two integral mounting tabs, and an integral hood-like water shield (4) that extends through a hole in the front door module carrier into the interior of the door cavity and protects the sensor orifice from contamination.
A cavity in the center of the molded plastic sensor housing contains the electronic circuitry of the sensor, which includes an electronic communication chip and the electronic pressure sensor. The housing cavity is filled with a potting material to seal and protect the internal electronic circuitry and components. A label on the sensor has a directional arrow and the word down imprinted upon it to provide verification of the correct sensor orientation in the vehicle. The pressure-type side impact sensors are each connected to the vehicle electrical system through a dedicated take out and connector of the front door wire harnesses.
The pressure-type side impact sensors cannot be repaired or adjusted and, if damaged or ineffective, they must be replaced.
The driver side seat belt switch is designed to control a path to ground for the seat belt switch sense input of the Occupant Restraint Controller (ORC). When the driver side front seat belt tip-half is inserted into the seat belt buckle, the switch closes the path to ground; and, when the driver side front seat belt tip-half is removed from the seat belt buckle, the switch opens the ground path. The switch is actuated by the latch mechanism within the seat belt buckle.
The seat belt switch is connected in series between ground and the seat belt switch sense input of the ORC. The ORC relays an electronic seat belt switch status message to other electronic modules in the vehicle over the Controller Area Network (CAN) data bus. The seat belt switch receives ground at all times through its pigtail wire connection to the seat wire harness from a take out of the body wire harness. An eyelet terminal connector on the body wire harness ground take out is secured beneath a ground screw to the body sheet metal.
The seat belt switch as well as the hard wired circuits between the switch and the ORC may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the electronic controls or communication between modules related to seat belt switch operation. The most reliable, efficient and accurate means to diagnose the seat belt switch requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.
Scheme 3
Seat belt retractor tensioners supplement the dual front airbag system for all versions of this vehicle. These tensioners are integral to the front seat belt and retractor units (1), which are secured to the B-pillars on the right and left sides of the vehicle. The retractors are concealed beneath the molded plastic B-pillar trim. The seat belt tensioner consists primarily of a molded plastic tensioner housing (3), a tubular metal piston housing (4), a piston, a short rack gear, a set of pinion gears and a pyrotechnically activated gas generator (2).
All of these components are located on one side of the retractor spool on the outside of the retractor housing. The seat belt tensioners are controlled by the Occupant Restraint Controller (ORC) and are connected to the vehicle electrical system through dedicated take outs of the body wire harness by keyed and latching molded plastic connector insulators to ensure a secure connection.
The retractor tensioners cannot be repaired and, if ineffective or damaged, the entire front seat belt and retractor unit must be replaced. The retractor tensioners are not intended for reuse and must be replaced following any front airbag deployment. A locked retractor that will not allow the seat belt webbing to be retracted or extracted is a sure indication that the seat belt tensioner has been deployed and requires replacement. Refer to RETRACTOR, Seat Belt , Removal .
The seat belt tensioners are deployed in conjunction with the dual front airbags by a signal generated by the Occupant Restraint Controller (ORC) through the driver or passenger seat belt tensioner line 1 and line 2 (or squib) circuits. When the ORC sends the proper electrical signal to the tensioners, the electrical energy generates enough heat to initiate a small pyrotechnic gas generator.
The gas generator is installed in one end of the tubular metal piston housing, which contains a piston and a small rack gear. As the gas expands, it pushes the piston and the rack gear through the tube. The rack gear engages a pinion gear that drives a gear set within the tensioner housing, which rotates the seat belt retractor spool causing slack to be removed from the front seat belt webbing.
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 injuries that the occupant might experience in these situations as a result of harmful contact with the steering wheel, steering column, instrument panel or windshield. Also, the seat belt retractor has a two-stage mechanism that is designed 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 ORC monitors the condition of the seat belt tensioners through circuit resistance, and will illuminate the airbag indicator in the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) and store a Diagnostic Trouble Code (DTC) for any fault that is detected. Proper diagnosis of the seat belt tensioner gas generator and squib circuits requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.