Part 3

Fig. 38 Passenger Airbag ON/OFF Switch:

PASSENGER AIRBAG ON/OFF SWITCH
The passenger airbag ON/OFF switch is standard equipment on all standard cab versions of this model when they are equipped with the dual front airbag system. This switch is a two-position, resistor multiplexed switch with a single integral red Light-Emitting Diode (LED), and a non-coded key cylinder-type actuator. The switch is located in the lower right corner of instrument panel center bezel, near the center of instrument panel to make the OFF indicator visible to all front seat occupants. When the switch is in its installed position, the only components visible through the dedicated opening of the cluster bezel are the switch face plate and nomenclature and the key cylinder actuator. The "OFF' position of the switch is illuminated when this switch position is selected, while the "ON" position of the switch is designated by text imprinted upon the face plate of the switch, but is not illuminated. The remainder of the switch is concealed behind the switch face plate and the instrument panel center bezel.

The passenger airbag ON/OFF switch housing is constructed of molded plastic and has three integral mounting tabs. These mounting tabs are used to secure the switch to the back of the molded plastic switch face plate with three small screws. The molded plastic face plate also has three integral mounting tabs that are used to secure the switch and face plate unit to the instrument panel center bezel with three additional screws. A molded plastic connector receptacle on the back of the switch housing connects the switch to the vehicle electrical system through a dedicated take out and connector of the instrument panel wire harness. The molded plastic harness connector insulator is keyed and latched to ensure proper and secure switch electrical connections. The passenger airbag ON/OFF switch cannot be adjusted or repaired and, if faulty or damaged, the switch must be replaced.

The passenger airbag ON/OFF switch allows the customer to turn the passenger airbag function ON or OFF to accommodate certain uses of the right front seating position where airbag protection may not be desired. See the owner's manual in the vehicle glove box for specific recommendations on when to enable or disable the passenger airbag. The OFF indicator of the switch will be illuminated whenever the switch is turned to the OFF position. The ignition key is the only key or object that should ever be inserted into the switch. The ON/OFF switch requires only a partial key insertion to fully depress a spring-loaded locking plunger. The spring-loaded locking plunger prevents the user from leaving the key in the switch. The key will be automatically ejected when force is not applied. To actuate the passenger airbag ON/OFF switch, insert the ignition key into the switch key actuator far enough to fully depress the plunger, then rotate the actuator to the desired switch position. When the switch key actuator is rotated to its clockwise stop (the key actuator slot will be aligned with the OFF indicator), the OFF indicator is illuminated and the passenger airbag is disabled. When the switch is rotated to its counterclockwise stop (the key actuator slot will be in a vertical position), the OFF indicator will be extinguished and the passenger airbag is enabled.

The passenger airbag ON/OFF switch connects one of two internal resistors in series between the passenger airbag mux switch sense and passenger airbag mux switch return circuits of the Airbag Control Module (ACM). The ACM continually monitors the resistance in these circuits to determine the switch position that has been selected. When the switch is in the OFF position, the ACM provides a ground input to the switch through the passenger airbag indicator driver circuit, which energizes the Light-Emitting Diode (LED) that illuminates the OFF indicator of the switch. The ACM will also illuminate the OFF indicator of the switch for about seven seconds each time the ignition switch is turned to the ON position as a bulb test. The ACM will also store a Diagnostic Trouble Code (DTC) for any fault it detects in the passenger airbag ON/OFF switch or indicator circuits, and will illuminate the airbag indicator in the instrument cluster if a fault is detected. For proper diagnosis of the passenger airbag ON/OFF switch or the ACM, a DRB III scan tool is required. Refer to the appropriate diagnostic information.

Fig. 46 Seat Belt Switch:

SEAT BELT SWITCH
The seat belt switch is a small, normally open, single pole, single throw, leaf contact, momentary switch. Only one seat belt switch is installed in the vehicle, and it is integral to the buckle of the driver side front seat belt buckle-half, located on the inboard side of the driver side front seat track. The seat belt switch is connected to the vehicle electrical system through a two-wire pigtail wire and connector on the seat belt buckle-half, which is connected to a wire harness connector and take out of the seat wire harness routed beneath the driver side front seat cushion in the passenger compartment.

The seat belt switch cannot be adjusted or repaired and, if faulty or damaged, the entire driver side front seat belt buckle-half 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 instrument cluster. When the driver side seat belt tip-half is inserted in the seat belt buckle, the switch closes the path to ground; and, when the driver side 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 instrument cluster. 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 on the left cowl side inner panel, beneath the instrument panel.

Fig. 47 Seat Belt Tensioner:

SEAT BELT TENSIONER
Front outboard seating position seat belt tensioners supplement the driver and passenger airbags for all versions of this model. The seat belt tensioner is integral to the front outboard seat belt and retractor unit, which is secured to the inner B-pillar on the right and left sides of the vehicle. The retractor is concealed beneath the molded plastic inner B-pillar trim. The seat belt tensioner consists primarily of a die cast aluminum tensioner housing or chamber, a mechanical clutch unit, a tape-like metal strip, a pair of cutters, a 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. The seat belt tensioner is controlled by the Airbag Control Module (ACM) and is 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 tensioner cannot be repaired and, if faulty or damaged, the entire outboard front seat belt and retractor unit must be replaced. If the front airbags have been deployed, the seat belt tensioners have also been deployed. The seat belt tensioner is not intended for reuse and must be replaced following a 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 RESTRAINTS/FRONT OUTBOARD SEAT BELT & RETRACTOR - REMOVAL).

The seat belt tensioners are deployed by a signal generated by the Airbag Control Module (ACM) through the driver and passenger seat belt tensioner line 1 and line 2 (or squib) circuits. When the ACM 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 at the top of the tensioner housing which contains a long metal tape that is routed through two chambers within the housing. Each end of the tape is wound around the outer sleeve of a mechanical clutch mechanism secured to one end of the torsion bar upon which the retractor spool is secured. As the gas expands, it is directed against the metal tape within the two chambers of the housing causing the tape to unwind from the clutch sleeve. As the clutch rotates it engages the torsion bar, which drives the seat belt retractor spool causing the slack to be removed from the seat belt.

Once a seat belt tensioning sequence has been completed, the forward momentum of the occupant results in deformation of the torsion bar. As the torsion bar deforms it allows the seat belt webbing to unwind from the retractor spool, which causes the metal tape to be wound back onto the clutch sleeve until it is pulled tight against two cutter blades within the housing, which immediately cut the metal tape.

Removing excess slack from the seat belt not only keeps the occupant 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 a harmful contact with the steering wheel, steering column, instrument panel and/or windshield. The torsion bar is designed to deform in order to control the loading being applied to the occupant by the seat belt 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 ElectroMechanical Instrument Cluster (EMIC) 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.

Fig. 47 Seat Belt Tensioner:

SEAT BELT TENSION REDUCER
A seat belt tension reducer is standard equipment for the driver side front outboard seat belt on standard cab versions of this model. The tension reducer is integral to the driver side front outboard seat belt and retractor unit, which is secured to the inner B-pillar on the left side of the vehicle. The retractor is concealed beneath the molded plastic inner B-pillar trim. The seat belt tension reducer consists primarily of a 12-volt Direct Current (DC) solenoid and an integral connector receptacle that is located on the forward facing end housing of the retractor. The seat belt tension reducer is controlled by a battery current output of the ignition switch and a ground path provided by the seat belt switch, and is 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 tension reducer cannot be repaired and, if faulty or damaged, the entire driver side front outboard seat belt and retractor unit must be replaced. (Refer to RESTRAINTS/ FRONT OUTBOARD SEAT BELT & RETRACTOR - REMOVAL).

The seat belt tension reducer is controlled by a ground signal received from the seat belt switch on the seat belt switch sense circuit and a battery current signal received from the ignition switch on the fused ignition switch output (run-accessory) circuit. When the seat belt switch is closed (the driver side front seat belt is fastened) and the ignition switch is in the ON or Accessory positions, the seat belt tension reducer solenoid is energized. When the solenoid is energized, it actuates a mechanism within the driver side front outboard seat belt retractor to reduce the normal recoil spring tension exerted by the retractor spool, which is designed to reel in the seat belt webbing onto the spool. When the driver side seat belt is unbuckled or if the ignition switch is turned to any position except On or Accessory, the tension reducer solenoid is de-energized and the normal recoil spring tension of the retractor is restored.

The action of the seat belt tension reducer results in improved seat belt comfort for the driver. Reducing the seat belt retractor recoil spring tension is desirable on standard cab models of this vehicle and not on the quad cab model due to the different mounting position required for the seat belt turning loop on the B-pillar relative to the driver's seat position on the standard cab model. The seat belt tension reducer may be diagnosed using conventional diagnostic tools and methods.

Fig.2 SRS Logo:

SIDE CURTAIN AIRBAG
Optional side curtain airbags are available for this model when it is also equipped with dual front airbags. These airbags are passive, inflatable, Supplemental Restraint System (SRS) components, and vehicles with this equipment can be readily identified by a molded identification trim button with the "SRS- AIRBAG" logo located on the headliner above each A-pillar, and above each B-pillar on quad cab models. This system is designed to reduce injuries to the vehicle occupants in the event of a side impact collision.

Vehicles equipped with side curtain airbags have two individually controlled curtain airbag units. These airbag units are concealed and mounted above the headliner where they are each secured to one of the roof side rails. Each folded airbag cushion is contained within a long extruded plastic channel that extends along the roof rail from the A-pillar at the front of the vehicle to just behind the B-pillar on standard cab models, and to just behind the C-pillar on quad cab models. A tether extends down the A-pillar from the front of the airbag cushion, where it is retained to the pillar with plastic push-in routing clips and it is secured to the base of the A-pillar near the belt line with a screw.

The hybrid-type inflator for each airbag is secured to the roof rail at the rear of the airbag unit behind the B-pillar (standard cab) or C-pillar (quad cab), and is connected to the airbag cushion by a long tubular manifold. The inflator bracket and the airbag cushion channel are located with plastic push-in fasteners to the roof rail, then secured with screws to spring nuts located in the roof rail. A two-wire take out of the body wire harness with a keyed and latched connector insulator connects directly to an integral receptacle on the inflator initiator.

The side curtain airbag unit cannot be adjusted or repaired and must be replaced if deployed, faulty, or in any way damaged. Once a side curtain airbag has been deployed, the complete airbag unit, the headliner, the upper A, B, and C-pillar trim, and all other visibly damaged components must be replaced.

Each side curtain airbag is deployed individually by an electrical signal generated by the left or right Side Impact Airbag Control Module (SIACM) 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 SIACM 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 bag taut, thus ensuring that the bag will deploy in the proper position. Following the airbag deployment, the airbag cushion quickly 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.

Fig. 53 Side Impact Airbag Control Module:

SIDE IMPACT AIRBAG CONTROL MODULE
On vehicles equipped with the optional side curtain airbags, a Side Impact Airbag Control Module (SIACM) and its mounting bracket are secured with four screws to the inside of each B-pillar behind (standard cab) or above (quad cab) the front outboard seat belt retractor, and concealed behind the B-pillar trim. Concealed within a hollow in the center of the die cast aluminum SIACM housing is the electronic circuitry of the SIACM which includes a microprocessor and an electronic impact sensor. The SIACM housing is secured to a die cast (standard cab) or stamped steel (quad cab) mounting bracket, which is unique for the right or left side application of this component. The SIACM should never be removed from its mounting bracket. The housing also receives a case ground through this mounting bracket when it is secured to the vehicle. A molded plastic electrical connector receptacle that exits the top of the SIACM housing connects the unit to the vehicle electrical system through a dedicated take out and connector of the body wire harness. Both the SIACM housing and its electrical connection are sealed to protect the internal electronic circuitry and components against moisture intrusion.

The impact sensor internal to the SIACM is calibrated for the specific vehicle, and is only serviced as a unit with the SIACM. The SIACM cannot be repaired or adjusted and, if damaged or faulty, it must be replaced.

The microprocessor in the Side Impact Airbag Control Module (SIACM) contains the side curtain airbag system logic circuits and controls all of the features of only the side curtain airbag mounted on the same side of the vehicle as the SIACM. The SIACM uses On-Board Diagnostics (OBD) and can communicate with other electronic modules in the vehicle as well as with the DRB III scan tool using the Programmable Communications Interface (PCI) data bus network. This method of communication is used by the SIACM to communicate with the Airbag Control Module (ACM) and for supplemental restraint system diagnosis and testing through the 16-way data link connector located on the driver side lower edge of the instrument panel. The ACM communicates with both the left and right SIACM over the PCI data bus.

The SIACM microprocessor continuously monitors all of the side curtain airbag electrical circuits to determine the system readiness. If the SIACM detects a monitored system fault, it sets an active and stored Diagnostic Trouble Code (DTC) and sends electronic messages to the ACM over the PCI data bus. The ACM will respond by sending an electronic message to the EMIC to turn on the airbag indicator, and by storing a DTC that will indicate whether the left or the right SIACM has stored the DTC that initiated the airbag indicator illumination. An active fault only remains for the current ignition switch cycle, while a stored fault causes a DTC to be stored in memory by the SIACM. For some DTCs, if a fault does not recur for a number of ignition cycles, the SIACM will automatically erase the stored DTC. For other internal faults, the stored DTC is latched forever.

The SIACM receives battery current on a fused ignition switch output (run-start) circuit through a fuse in the Integrated Power Module (IPM). The SIACM has a case ground through its mounting bracket and also receives a power ground through a ground circuit and take out of the body wire harness. This take out has a single eyelet terminal connector that is secured by a ground screw to the body sheet metal. These connections allow the SIACM to be operational whenever the ignition switch is in the Start or On positions. An electronic impact sensor is contained within the SIACM. The electronic impact sensor is an accelerometer that senses the rate of vehicle deceleration, which provides verification of the direction and severity of an impact. A pre-programmed decision algorithm in the SIACM microprocessor determines when the deceleration rate as signaled by the impact sensor indicates a side impact that is severe enough to require side curtain airbag protection. When the programmed conditions are met, the SIACM sends the proper electrical signals to deploy the side curtain airbag.

The hard wired inputs and outputs for the SIACM may be diagnosed and tested using conventional diagnostic tools and procedures. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the SIACM, the PCI data bus network, or the electronic message inputs to and outputs from the SIACM. The most reliable, efficient, and accurate means to diagnose the SIACM, the PCI data bus network, and the electronic message inputs to and outputs from the SIACM requires the use of a DRB III scan tool. Refer to the appropriate diagnostic information.