Air Bag and Safety Belt Pretensioner (SRS) Componants

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 three-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, also driver and passenger safety belt retractor pretensioners. This vehicle can also be equipped with optional seat side air bags. In addition, this vehicle line is equipped with:
- a front impact severity sensor, mounted on the radiator opening grille panel.
- side impact sensors (when equipped with seat side air bags), located on the rocker panel near the base of the B-pillars.
- a driver seat position sensor, mounted to the driver seat track.
- usage detection switches that are part of the driver and front passenger safety belt buckles.
- a safety belt tension sensor that is part of the front passenger safety belt buckle.
- an occupant classification sensor (OCS) system, located in the front passenger seat cushion.

Air Bag And Safety Belt Pretensioner Supplemental Restraint System (SRS) Components - Illustration 1 Of 2 (Part 1):

Air Bag And Safety Belt Pretensioner Supplemental Restraint System (SRS) Components - Illustration 1 Of 2 (Part 2):

Air Bag And Safety Belt Pretensioner Supplemental Restraint System (SRS) Components - Illustration 2 Of 2 (Part 1):

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

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

Driver Air Bag Module

CAUTION: Always apply a liberal bead of electrical grease XG-12 to the driver air bag module electrical connector face prior to connecting the driver air bag module electrical connector to the clockspring. Failure to follow this instruction may result in poor connectivity and may set intermittent/on-demand supplemental restraint system (SRS) DTCs.

NOTE: The air bag supplemental restraint system (SRS) utilizes DC firing for air bag and pretensioner deployment.

The driver air bag module:
- is installed new as an assembly.
- is mounted in the center of the steering wheel.
- will deploy upon receiving a flow of current from the restraints control module (RCM).

Electrical System
The electrical system that supports the air bag 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).

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:
- ABS module
- data link connector (DLC)
- generic electronic module (GEM)
- instrument cluster module
- occupant classification sensor (OCS) system
- powertrain control module (PCM)
- restraints control module (RCM)

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 two 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) for additional information.

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 scan 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 precautions must be taken before rezeroing of 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 five 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 NGS+ (NGS with Vehicle Communication Module (VCM) and the latest software update) to rezero the OCS system:
- select "FUNCTION TESTS"
- select "SYSTEM RESET"
- 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 display "TEST/FUNCTION SUCCESSFUL" once rezeroing of the OCS system is complete.

NOTE: To rezero the OCS system using the Worldwide Diagnostic System (WDS):
- elect 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.

NOTE:
- To identify between a production OCS system and a OCS system service kit, inspect the OCS ECU electrical connector.

A production OCS system allows disconnection of the electrical connector from the OCS electronic control unit (ECU).

An OCS system service kit (OCS service kit) has the OCS ECU electrical connector glued to the ECU, it cannot and should not be disconnected or altered. An OCS system service kit also has an in-line 10-pin connector between the OCS ECU and the seat wiring harness.

- If the first attempt to rezero the OCS system is unsuccessful, a second attempt must be made.

The seat occupant classification sensor system is found only on the front passenger seat. The front passenger seat occupant classification sensor (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 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 pressure sensor, then electronically communicated to the OCS electronic control unit. Based on programmed limits, the OCS electronic control unit will inform the restraints control module (RCM), via the 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 system components (seat pan, 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 pan, seat cushion foam pad, bladder with pressure sensor and electronic control unit) must be installed as an assembly.

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

Passenger Air Bag And PAD Indicator Status:

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 part of the hazard switch, 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 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 SRS defaults the passenger air bag module to enabled status regardless of the size of the occupant in the front outboard passenger seat. The PAD indicator will be unlit.

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

Passenger Air Bag Module

NOTE: The air bag supplemental restraint system (SRS) utilizes DC firing for air bag and pretensioner deployment.

The passenger air bag module:
- is installed new as an assembly.
- is mounted in the passenger side of the instrument panel.

Restraints Control Module (RCM)

WARNING: The 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.

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 air bag supplemental restraint system (SRS) utilizes DC firing for air bag and pretensioner deployment.

The restraints control module carries out the following functions:
- deploys the air bag(s) in the event of a deployable crash.
- activates the safety belt retractor pretensioners to remove slack from the safety belt.
- monitors the SRS for faults.
- communicates to the instrument cluster module, over the HS-CAN bus, to illuminate the air bag indicator if a fault is detected.
- communicates over the HS-CAN bus through the data link connector (DLC) the current or historical diagnostic trouble codes (DTCs).

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 communicate over the HS-CAN bus to the instrument cluster to 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 six seconds and then off for two seconds. After the prove out, the air bag indicator will then remain lit if a SRS fault exists and will remain illuminated for the rest of the key cycle. The RCM will also communicate, over the HS-CAN bus, the current and historical DTCs through the DLC to the scan tool. If the air bag indicator does not function and the system detects a fault condition, the RCM will signal the instrument cluster module to activate an audible chime, located in the GEM. The chime is a series of five sets of five 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 150 ms of backup power to deploy the front air bags and pretensioners 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 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 restraints control module (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 additional information.

Safety Belt Pretensioners

NOTE: The air bag supplemental restraint system (SRS) utilizes DC firing for air bag and pretensioner deployment.

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 restraints control module (RCM) when the module detects a crash event force exceeding a programmed limit.

Safety Belt Tension Sensor
The safety belt tension sensor:
- is part of the front passenger safety belt buckle assembly.
- 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, when the child safety seat is installed according to manufacturer instructions. 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
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. The seat track position sensor is serviced with the seat track assembly. To install a new seat track position sensor, refer to Seats.

Impact Sensors

WARNING: Vehicle sensor orientation is critical for correct system operation. If a vehicle equipped with an air bag supplemental restraint system (SRS) is involved in a collision, inspect the sensor mounting bracket and wiring pigtail for deformation. Install and correctly position a new sensor or any other damaged supplemental restraint system (SRS) components whether or not the air bag is deployed.

For these vehicles, the SRS may use up to three satellite sensors in addition to the RCM. The RCM is mounted to the center tunnel between the front seats under the center console. All vehicles will have a front impact severity sensor and it is located in the front-center of the vehicle, mounted on the radiator support bracket. Vehicles equipped with seat side air bags are equipped with two side impact sensors, located on the rocker panel near the base of the B-pillars. Mounting orientation is critical for correct operation of all impact sensors.