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

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

The air bag supplemental restraint system (SRS) is designed to provide increased collision protection for front seat and second row outboard occupants, in addition to that provided by the 3-point safety belt system. Safety belt use is necessary to obtain the best occupant protection and to receive the full advantage of the SRS.

This vehicle line contains dual stage deployment (advanced restraint system) driver and front passenger air bag modules. These vehicles are also equipped with driver and front passenger safety belt retractor pretensioners. These vehicles can also be equipped with optional side air curtains that deploy from the A-pillar to the C-pillar upon a side impact. Vehicles with optional side air curtains are also equipped with seat side air bag modules in the front seats.

Side air curtains deploy from the headliner, protecting the first and second row outboard occupants during a side impact. Seat side air bag modules deploy from the outboard front seat backrest upon a side impact. In addition, a front impact severity sensor is mounted to the lower radiator support, a seat position sensor is mounted to the driver seat and a usage detection switch is added to the front driver and passenger outboard buckles. If equipped with optional side air curtain modules and seat side air bag modules, there are an additional 4 side impact sensors.

Vehicles are also equipped with an occupant classification sensor (OCS) system as part of the front passenger seat. The OCS system includes 2 OCS rails and an OCS module.

Air Bag And Safety Belt Pretensioner Supplemental Restraint System (SRS) Components (Part 1):

Air Bag And Safety Belt Pretensioner Supplemental Restraint System (SRS) Components (Part 2):

Clockspring
The clockspring:
- is mounted on the steering column, behind the steering wheel.
- continuously transfers electrical signals from the driver air bag module to the restraints control module (RCM).

Driver Air Bag Module
The driver air bag module:
- contains dual stage deployment (advanced restraint system).
- is installed new as an assembly.
- is mounted in the center of the steering wheel.

Driver Seat Side Air Bag Module

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

A seat side air bag module provides protection of the thorax area (between the neck and abdomen) of the body, working in conjunction with the head protection provided by a side air curtain module (if equipped).

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.
- is used in conjunction with a side air curtain module.

High Speed Controller Area Network (HS-CAN)
This vehicle utilizes a communication system called a high-speed controller area network (HS-CAN). The HS-CAN consists of a twisted pair of wires connected to the following:
- Anti-lock brake system (ABS) module
- Instrument cluster module
- Occupant classification sensor (OCS) module
- Powertrain control module (PCM)
- Transmission control module (TCM)
- Restraints control module (RCM)
- Data link connector (DLC)

The HS-CAN circuits use a bias voltage of approximately 2.5 volts, one is a positive 2.5 volts while the other is a negative 2.5 volts. The HS-CAN also uses 2 terminating resistors, one contained within the PCM, the other in the instrument cluster module. The terminating resistors are not serviced separately. The terminating resistors have a value of 120 ohms each, for a total normal operating system total of 60 ohms. The HS-CAN will operate with only one terminating resistor and has the capability to communicate some messages to some of the control modules with only one circuit functioning, but at a reduced rate of performance. Refer to Information Bus (Module Communications Network).

Occupant Classification Sensor System
The occupant classification sensor system is found only on the front passenger seat. The front passenger OCS system is comprised of 2 OCS rails (weight sensors) that are mounted to each side of the seat track and an OCS module (electronic control unit) which is mounted to the electrical bracket underneath the seat cushion pan. The weight of any occupant or object on the front passenger seat is The weight is then electronically communicated to the OCS module.

The OCS system is also used for operation of the passenger Belt Minder. For additional information on the passenger Belt Minder feature, refer to Seat Belt Systems. To deactivate or reactivate the passenger Belt Minder feature, refer to Seat Belt Systems or the owner's literature.

The components that make up the OCS system, OCS module, inboard OCS rail and outboard OCS rail are serviced separately.

When the front passenger seat is removed for service, the Zero Seat Weight Test must be carried out after the installation of the front passenger seat. When a OCS system component is installed new, the System Reset must be carried out after the installation of the front passenger seat. The Zero Seat Weight Test and/or System Reset must be carried out only as instructed to do so.

OCS System Module
Based on programmed limits, the OCS module 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 or passenger seat side air bag module is to be deployed in the event of a deployable collision.

The OCS module monitors the OCS system for faults and communicates on-demand and continuous Diagnostic Trouble Codes (DTCs) via the data link connector (DLC) with the use of a diagnostic tool.

The components that make up the OCS system, OCS system module, inboard OCS rail and outboard OCS rail are serviced separately.

OCS Rails (Weight Sensors)







The components that make up the OCS system (OCS system module, inboard OCS rail and outboard OCS rail) are serviced separately.

Passenger Air Bag Module
The passenger air bag module:
- contains dual stage deployment (advanced restraint system).
- is installed new as an assembly.
- is mounted in the passenger side of the instrument panel.

Passenger Air Bag Deactivation (PAD) Indicator
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 a stand-alone lamp installed into the vehicle instrument panel 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 disabled. An exemption to this is when the front passenger seat is determined to be empty and passenger safety belt buckle unbuckled, and therefore indication of a deactivated passenger air bag module is not necessary. In all other cases, the PAD indicator is unlit when the passenger air bag module is enabled.

When the ignition switch is in the ON 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 correct functional operation of the PAD indicator.

The PAD indicator will be lit/unlit within 1.0 to 1.5 seconds of a change of state from the OCS system.

When an OCS system fault is present, the RCM defaults the passenger air bag module to the last valid state received from the OCS system until the ignition switch is turned OFF. If the OCS system fault is still present when the ignition switch is turned ON, the RCM defaults the passenger air bag module to enabled regardless of the size of occupant in the front passenger seat. The PAD indicator will be unlit.

Passenger Air Bag And PAD Indicator Status:

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

Passenger Seat Side Air Bag Module

NOTE:
- References to seat 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.
- When servicing a seat equipped with a seat side air bag module, refer to Seats.

A seat side air bag module provides protection of the thorax area (between the neck and abdomen) of the body, working in conjunction with the head protection provided by a side air curtain module.

The passenger seat 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.
- is used in conjunction with a side air curtain module.

Restraints Control Module (RCM)

WARNING: The restraints control module (RCM) orientation is critical for correct system operation. If a vehicle equipped with an air bag supplemental restraint system (SRS) has been involved in a collision in which the center tunnel area has been damaged, inspect the mounting and bracket for deformation. If damaged, a new RCM must be installed whether or not the air bags have deployed. In addition, make sure the area of the RCM mounting is restored to its original condition.

CAUTION:
- Prior to removal of the module, it is necessary to upload module configuration information to the diagnostic tool. This information needs to be downloaded into the new module once installed.
- When installing a new restraints control module (RCM), always make sure the correct RCM is being installed. The RCM 40-pin connector is keyed differently for vehicles with side air curtains and side air bags than the 40-pin connector for vehicles without side air curtains and side air bags. Do not force the 40-pin connector onto the RCM. If the connector is forced onto the RCM, damage to the RCM and/or connector will occur.

NOTE: When installing a new restraints control module (RCM), always make sure the correct RCM is being installed. If an incorrect RCM is installed, erroneous DTCs will result.

The RCM carries out the following functions:
- deploys the air bag(s) in the event of a deployable crash.
- activates the safety belt buckle pretensioner and safety belt adaptive load limiting retractor to control tension on the safety belt.
- monitors the SRS for faults.
- illuminates the air bag indicator if a fault is detected.
- communicates through the data link connector (DLC) the on-demand or continuous Diagnostic Trouble Codes (DTCs).
- signals the instrument cluster module to activate a chime if the air bag indicator is not available and another SRS fault exists.

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

When the ignition is cycled (turned OFF and then ON), the air bag indicator will prove out by lighting for 6 seconds and then off. If a SRS fault exists, the air bag indicator will illuminate and remain illuminated for the rest of the key cycle. The RCM will also communicate the on-demand (current) and continuous (historical) DTCs through the DLC, to the diagnostic tool. If the RCM requests illumination of the air bag indicator and the air bag indicator does not function, the instrument cluster module will automatically activate an audible chime. The chime is a series of 5 sets of 5 tone bursts. If the chime is heard, the SRS and the air bag indicator require repair.

The RCM includes a backup power supply. This feature provides sufficient backup power to deploy the air bags in the event that the ignition circuit is lost or damaged during impact. The backup power supply will deplete its stored energy approximately one minute after the battery ground cable is disconnected.

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

Safety Belt Buckle Switches
As part of the supplemental restraint system (SRS), the front safety belt buckles are equipped with safety belt buckle switches. The safety belt buckle switches are comprised of integrated circuits called Hall-effect sensors. The safety belt buckle switches (Hall-effect sensors) are located in the driver and passenger safety belt buckles. The safety belt buckle switches indicate to the RCM whether the safety belts are connected or disconnected. The RCM uses this information in determining the deployment rate of the dual-stage driver and passenger air bag modules. The RCM also communicates the driver safety belt buckle switch status to the instrument cluster module, which monitors the information to control the safety belt warning indicator. Refer to Instrument Panel, Gauges and Warning Indicators for information on the instrument cluster module.

Side Air Curtain Module

WARNING: Anytime the side air curtain has deployed, the headliner, and all A-, B-, C-pillar upper trim panels and attaching hardware must be replaced along with any other damaged components and hardware. Failure to do so can result in personal injury in the event of a side air curtain deployment.

The side air curtain module:
- is installed as an assembly.
- is mounted above the headliner.
- attaches from the A-pillar frame to the C-pillar frame.

Seat Track Position Sensor
The seat track position sensor is a Hall-effect sensor located on the driver seat track. The seat track position sensor informs the restraints control module (RCM) of the driver seat position. Based on programmed limits, the seat track position sensor will inform 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.

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 restraints control module (RCM) to the SRS components.
- provides the electrical path from the RCM to the data link connector (DLC).
- provides the electrical path (via HS-CAN) from the RCM to the instrument cluster module.

Sensors

WARNING:
- The restraints control module (RCM) orientation is critical for correct system operation. If a vehicle equipped with an air bag supplemental restraint system (SRS) has been involved in a collision in which the center tunnel area has been damaged, inspect the mounting and bracket for deformation. If damaged, a new RCM must be installed whether or not the air bags have deployed. In addition, make sure the area of the RCM mounting is restored to its original condition.
- Vehicle sensor orientation is critical for correct system operation. If a vehicle equipped with an SRS is involved in a collision, inspect the sensor mounting bracket and wiring pigtail for deformation. Replace and correctly position the sensor or any other damaged SRS components whether or not the air bag is deployed.

For these vehicles, the SRS uses up to 5 satellite sensors in addition to the RCM. The RCM is mounted to the center tunnel beneath the console. All vehicles will have one front impact severity sensor located in the front-center area of the vehicle, behind the grille mounted on the radiator support. The first row impact sensors are located on each of the B-pillars behind the trim panel, the second row sensors are located on each C-pillar. Mounting orientation is critical for correct operation of all impact sensors.