Air Bag and Safety Belt Pretensioner Supplemental Restraint System (SRS) Components

AIR BAG AND SAFETY BELT PRETENSIONER SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

Air Bag And Safety Belt Pretensioner Supplemental Restraint System (SRS) Deployable Components:

Air Bag And Safety Belt Pretensioner Supplemental Restraint System (SRS) Sensing Components:

The air bag and safety belt pretensioner supplemental restraint system (SRS) is designed to provide increased collision protection for front seat occupants in addition to that provided by the three-point safety belt system. Safety belt use is necessary to obtain the best occupant protection and to receive the full advantages of the SRS.

The air bag and safety belt pretensioner supplemental restraint system (SRS) components are shown in the illustration.

Driver Air Bag Module

NOTE: References to the driver air bag module must not be confused with the side (seat-mounted) air bag components of the supplemental restraint system (SRS).

The driver air bag module:
- is steering wheel mounted.
- is a dual-stage air bag, deploying at one of two different rates depending upon impact severity, safety belt usage, and driver seat position.
- will deploy upon receiving a flow of current from the restraints control module (RCM).
- has no subassemblies.

Clockspring
The clockspring:
- is mounted on the steering column, behind the steering wheel.
- allows continuous electrical contact between the RCM and the driver air bag module when the steering wheel is turned.

Driver Seat Side Air Bag Module

NOTE:
- References to side air bag modules refer to the seat-mounted and not to the steering wheel or instrument panel mounted air bag components of the SRS.
- For additional information, when servicing a seat equipped with a side air bag module, refer to Seats.

The driver seat side air bag module:
- will deploy upon receiving a flow of current from the RCM initiated by the driver seat side impact sensor and internal RCM circuitry.
- is installed as an assembly.
- is mounted in the driver seat back.

Passenger Air Bag Module

NOTE: References to side air bag modules refer to the seat-mounted and not to the steering wheel or instrument panel mounted air bag components of the SRS.

The passenger air bag module:
- is a dual-stage air bag, deploying at one of two different rates depending upon impact severity and safety belt usage.
- will deploy upon receiving a flow of current from the RCM.
- is installed as an assembly.
- is mounted in the right side of the instrument panel.

Passenger Seat Side Air Bag Module

NOTE:
- References to side air bag modules refer to the seat-mounted and not to the steering wheel or instrument panel mounted air bag components of the SRS.
- For additional information, when servicing a seat equipped with a side air bag module, refer to Seats.

The passenger side air bag module:
- will deploy upon receiving a flow of current from the RCM initiated by the passenger seat side impact sensor and internal RCM circuitry.
- is installed as an assembly.
- is mounted in the passenger seat back.

Safety Belt Buckle Switch
As part of the supplemental restraint system (SRS), the driver and passenger safety belt buckles are equipped with a hall-effect switch. The safety belt buckle switches indicate to the restraints control module (RCM) whether the safety belt buckles are buckled or unbuckled.

The RCM uses this information in determining the deployment rate of the dual-stage driver and passenger air bag modules.

The safety belt buckle switches are also used for the driver safety belt warning system and the driver and passenger belt minder.

Safety Belt Pretensioners
As part of the SRS the safety belt buckles are equipped with pretensioners. The pretensioners remove excess slack from the safety belt webbing. The pretensioners are activated by the RCM when the module detects an impact event force exceeding a programmed limit.

Occupant Classification Sensor

CAUTION:
- It is necessary to rezero the OCS system when a front passenger seat cushion is disassembled, a new trim cover installed, or an OCS service kit is installed. A diagnostic tool is used to trigger the active command to carry out rezeroing of the OCS system.
- Make sure the seat is completely assembled before rezeroing.
- The following precautions must be taken before rezeroing the OCS system:
- Make sure the OCS system components are connected and no faults are present.
- Make sure the OCS system is not at a temperature below 0°C (32°F) or above 45°C (113°F) when initiating the rezeroing process. If the vehicle has been exposed to extreme cold or hot temperatures, the vehicle must be exposed and kept at a temperature within the limits, 0°C to 45°C (32°F to 113°F) for a minimum of 30 minutes.
- Make sure nothing is present on the passenger seat before rezeroing and nothing is placed on the seat during the rezeroing process.
- Make sure a minimum eight second time period has passed after cycling the ignition switch ON before the rezeroing process.

NOTE:
- For best results in rezeroing, the OCS system should be at or near room temperature, 10°C to 29°C (50°F to 85°F).
- When using a New Generation STAR (NGS) Tester you must use the appropriate memory card with the latest update to carry out this function. To rezero the OCS system:
- select "SERVICE BAY FUNCTIONS"
- select "RCM"
- select "SYSTEM RESET"
- select the vehicle from the menu
- view the on-screen information, then press "TRIGGER"

The NGS screen will then display "OCS RESET: REZERO." Press "DONE" (button 8) to rezero the OCS system. The NGS will return to the vehicle menu once rezeroing of the OCS system is complete.

- To rezero the OCS system using the Worldwide Diagnostic System (WDS):
- select the "Toolbox" icon
- select "Body" from the menu
- select "Restraints" from the menu
- select "Seat Weight Sensor ReZero"

After selecting "Seat Weight Sensor ReZero", follow the on-screen prompts to carry out rezeroing of the OCS system.

- The ignition switch must be cycled after rezeroing the OCS system.
- If the first attempt to rezero the OCS system is unsuccessful, a second attempt must be made.

The seat occupant classification sensor (OCS) system is found only on the front passenger seat. The front passenger seat OCS system is comprised of a silicone gel-filled bladder mounted in the seat cushion, a pressure sensor that is mounted to the seat frame and an electronic control unit which is also mounted to the seat frame. Pressure is applied to the OCS system bladder when weight of any occupant or object in the front passenger seat is present. The pressure is then transferred through a tube, is sensed by the OCS system pressure sensor, then electronically communicated to the OCS system electronic control unit (ECU). Based on preprogrammed set points the OCS system ECU will inform the restraints control module (RCM), via a high-speed controller area network (HS-CAN), of the necessary information. The RCM uses this information in determining if the passenger air bag module is to be deployed in the event of a deployable collision. The RCM may also use this information to illuminate/not illuminate the passenger air bag deactivation (PAD) indicator.

When an OCS system fault is present, the air bag indicator lamp will illuminate or the air bag warning chime will be activated (if an air bag indicator fault is present). The SRS then defaults the passenger air bag module to ON (activated) regardless of the size of the occupant in the front outboard passenger seat.

The OCS system components (seat cushion foam pad, bladder with pressure sensor and electronic control unit) are calibrated to each other and are serviced as an assembly. OCS system components are not to be installed separately. If installing a new OCS system, OCS system component or seat cushion foam pad, a new OCS system service kit (seat cushion foam pad, bladder with pressure sensor and electronic control unit) must be installed as an assembly.

The OCS system also interprets a variable voltage signal provided by the safety belt tension sensor to identify the presence of a child safety seat in the front outboard passenger seat. The OCS system then communicates with the restraints control module (RCM), automatically deactivating the passenger air bag module.

Passenger Air Bag Deactivation (PAD) Indicator

CAUTION: The passenger air bag deactivation (PAD) indicator is part of integrated control panel (ICP) assembly and cannot be separately serviced. Installation of an incorrect ICP may cause a fault in the supplemental restraint system and illuminate the air bag warning indicator in the instrument cluster.

The passenger air bag deactivation (PAD) indicator is a visual indicator used to inform the front seat occupants of the passenger air bag deactivation state. The PAD indicator is located in the integrated control panel (ICP) in a position visible to each front seat occupant.

The restraints control module (RCM) controls the state of the PAD indicator through a direct hardwire connection, based on information provided by the occupant classification sensor (OCS) system. The PAD indicator is lit to indicate the passenger air bag module is deactivated (OFF). Some exceptions to this are made in certain scenarios such as when the front passenger seat is determined to be empty, and therefore indication of a deactivated passenger air bag module is not necessary. In all cases the PAD indicator is unlit when the passenger air bag module is activated (ON).

When the ignition switch is in the RUN position, the PAD indicator prove-out period is initiated by the RCM. The RCM briefly activates the PAD indicator to prove-out the indicator function and verify to the front occupants proper functional operation of the PAD indicator.

The PAD indicator will illuminate/not illuminate within 1.0 ± 0.5 seconds of a change of state from the OCS system.

When an OCS system fault is present the SRS defaults the passenger air bag module to ON (activated) regardless of the size of the occupant in the front outboard passenger seat. The PAD indicator will be unlit.

Passenger Air Bag And PAD Indicator Status:

The table indicate the passenger air bag status and the PAD indicator status based the size of the front outboard passenger occupant.

Safety Belt Tension Sensor
The safety belt tension sensor:
- is part of the front outboard passenger safety belt and retractor assembly.
- is located at the safety belt anchor point.
- is used in conjunction with the occupant classification sensor (OCS) system.
- is a three-wire Hall-effect sensor that is part of the front passenger safety belt and retractor assembly.

The safety belt tension sensor is used by the OCS system to identify the presence of a child safety seat on the front outboard passenger seat. The safety belt tension sensor senses the tension on the safety belt assembly then provides an output to the OCS system electronic control unit (ECU), indicating that the safety belt assembly is cinched. After sensing the weight applied to the seat by the occupant and using the safety belt tension sensor input, the OCS system determines how the occupant should be classified and communicates this information to the restraints control module (RCM). If the occupant is classified to be a child, the RCM will then automatically deactivate the passenger air bag module.

Seat Track Position Sensor

NOTE: The seat track position sensor on a power seat is serviced as an assembly with the power seat track.

The seat track position sensor informs the RCM of the driver seat position. The RCM uses this information in determining the deployment rate of the dual-stage driver air bag module.

Restraints Control Module (RCM)

NOTE: Care must be taken when disconnecting and connecting the RCM electrical connectors.

The RCM is mounted on the center tunnel under the instrument panel. The RCM carries out the following functions:
- deploys the air bags in the event of a deployable impact.
- activates the safety belt buckle pretensioners to remove slack from the safety belt webbing.
- monitors the SRS for faults.
- illuminates the restraints indicator lamp (RIL) if a fault is detected.
- illuminates the passenger air bag deactivation (PAD) indicator when conditions warrant illumination.
- flashes the restraints indicator lamp to indicate the lamp fault code (LFC) detected.
- communicates through the data link connector (DLC) the current or historical diagnostic trouble codes (DTCs).
- signals the instrument cluster module to activate a chime if the restraints indicator lamp is not available and another SRS fault exists.
- records deployable and non-deployable impact data.

The RCM monitors the SRS for possible faults. If a fault is detected while the ignition switch is in the RUN position, the RCM will illuminate the restraints indicator lamp located in the instrument cluster.

When the ignition is cycled (turned off and then on), the restraints indicator lamp will remain lit for six seconds and then go out. If an SRS fault exists, the restraints indicator lamp will then flash the two-digit lamp fault code (LFC) associated with that fault. The restraints indicator lamp will flash the LFC five times, then remain illuminated for the rest of the key cycle. The RCM will communicate current and history diagnostic trouble codes (DTCs) through the data link connector (DLC) using a diagnostic tool. If the restraints indicator lamp does not function, and the RCM detects a fault condition, the RCM will signal the instrument cluster module to activate an audible chime. The chime is a series of five sets of five tone bursts. If the chime is heard, the SRS and the restraints indicator lamp require service.

LFCs are prioritized. If two or more faults occur at the same time, the fault having the highest priority will be displayed first. After that fault has been corrected, the next highest priority fault will be displayed.

The RCM includes a backup power supply. This feature provides sufficient power to deploy the front air bags and the safety belt buckle pretensioners in the event that the ignition circuit is damaged in a collision before the air bags are deployed. Once ignition voltage is removed the backup power supply will deplete its stored energy reserve in approximately one minute. The battery ground cable must be removed before deactivating a SRS.

Electrical System
The electrical system that supports the air bag supplemental restraint system (SRS):
- is powered from the battery through the ignition circuit.
- provides the electrical path from the RCM to the SRS components.
- provides the electrical path from the RCM to the restraints indicator lamp.
- provides the electrical path from the RCM to the data link connector (DLC).
- provides the electrical path from the RCM to the instrument cluster module.

Impact Sensors

WARNING: Mounting orientation of the impact sensors and the RCM is critical for correct system operation. If a vehicle has been involved in a collision in which the center tunnel area has been damaged, inspect the RCM mounting area for deformation. Inspect the impact sensor mounting area for damage. If damaged, a new RCM and sensors must be installed whether or not the air bags have deployed. In addition, make sure the mounting area of the RCM and impact sensors are restored to the original production configuration.

The impact sensors provide data to the RCM for use in calculating impact severity. This is accomplished using various electrical sensors located throughout the vehicle. A front impact severity sensor is located in the front-center of the vehicle, behind the grille. In addition on vehicles equipped with seat side air bags, there are side impact sensors located near the base of each B-pillar.