Air Bag and Safety Belt Pretensioner SRS

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

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

SRS Deployable Components

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

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

Air Bag And Safety Belt Pretensioner Supplemental Restraint System (SRS) Occupant Classification Sensor:

SRS Sensor Components

The air bag 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 advantage of the SRS.

Driver Air Bag Module
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 signal from the Restraints Control Module (RCM).
^ has no subassemblies.

Clockspring
The clockspring:
^ is mounted on the steering column, behind the steering wheel.
^ provides a continuous electrical path from the driver air bag module to the restraints control module (RCM).

Passenger Air Bag Module
The passenger air bag module:
^ is a dual-stage air bag, deploying at one of two different rates depending upon impact severity, safety belt usage, and passenger seat occupant classification (if equipped with a passenger seat occupant sensor).
^ is installed as an assembly.
^ is mounted in the passenger side of the instrument panel.

Safety Belt Pretensioners
As part of the supplemental restraint system (SRS), the safety belt retractors are equipped with pretensioners. The belt retractor pretensioners rotate the safety belt retractors to remove excess slack from the safety belt webbing. The pretensioners are activated by the restraints control module (RCM) when the module detects a frontal impact force exceeding a programmed limit.

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. Safety belt buckle switches are used to indicate to the restraints control module (RCM) whether the safety belts are buckled or unbuckled. The RCM uses this information in determining the deployment rate of the dual-stage driver and passenger air bag modules.

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 restraints control module (RCM) of the driver seat position. The RCM uses this information in determining the deployment rate of the dual-stage driver air bag module.

Occupant Classification Sensor

CAUTION: If replacing only the front passenger seat cushion trim cover, the seat occupant classification sensor must be rezeroed.

The seat occupant classification sensor is found only on the front passenger seat and is not equipped on all vehicles. A white tag having the letters "OCS" (occupant classification sensor) will appear under the front of the passenger seat to identify a seat equipped with a seat occupant sensor. When servicing a passenger seat equipped with a seat occupant sensor, the supplemental restraint system (SRS) must be deactivated according to Supplemental Restraint System (SRS) Deactivation and Reactivation in the General Procedures portion.

The front passenger seat Occupant Classification Sensor (OCS) 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 a High Speed Controller Area Network (CAN) if the passenger air bag module is to be deactivated. The RCM uses this information in determining if the passenger air bag module is to be deployed in the event of a deployable collision.

Restraints Control Module (RCM)

WARNING: THE RESTRAINTS CONTROL MODULE (RCM) ORIENTATION IS CRITICAL FOR CORRECT AIR BAG SUPPLEMENTAL RESTRAINT SYSTEM (SRS) OPERATION. IF A VEHICLE EQUIPPED WITH AN (SRS) SYSTEM HAS BEEN INVOLVED IN A COLLISION IN WHICH THE CENTER TUNNEL AREA HAS BEEN DAMAGED, INSPECT THE MOUNTING AND BRACKET FOR DEFORMATION. IF DAMAGED, THE RCM MUST BE REPLACED WHETHER OR NOT THE AIR BAGS HAVE DEPLOYED. IN ADDITION, MAKE SURE THE AREA OF THE RCM MOUNTING IS RESTORED TO ITS ORIGINAL CONDITION.

The restraints control module (RCM) is mounted on the center tunnel under the instrument panel. The RCM performs the following functions:
^ signals the inflators to deploy the air bags in the event of a deployable crash.
^ activates the safety belt retractor pretensioners to remove slack from the safety belt.
^ monitors the air bag supplemental restraint system (SRS) for faults.
^ illuminates the air bag indicator if a fault is detected.
^ flashes the air bag indicator 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 to activate a chime if the air bag indicator is not available and another SRS fault exists.
^ contains an internal safing sensor which is not serviced separately.

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 air bag indicator located in the instrument cluster.

When the ignition is cycled (turned off and then on), the air bag indicator will remain lit for six seconds and then go out. If an SRS fault exists, the air bag indicator will then flash the two-digit LFC. The air bag indicator will flash the LFC five times, then it will remain illuminated for the rest of the key cycle. The RCM will also communicate the current and historical DTCs through the data link connector (DLC), using 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 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 air bag indicator require repair.

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 backup power to deploy the air bags in the event that the ignition circuit is damaged in a collision before the safing and air bag sensors determine that an air bag deployment is required. The backup power supply will deplete its stored energy approximately one minute after the battery ground cable is disconnected.

Electrical System
The electrical system that supports the air bag supplemental restraint system (SRS):
^ is powered by 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 air bag indicator.
^ provides the electrical path from the RCM to the data link connector (DLC).
^ provides the electrical path from the RCM to the instrument cluster.

Impact 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 RIGHT COWL A-PILLAR AREA HAS BEEN DAMAGED, INSPECT THE MOUNTING AND BRACKET FOR DEFORMATION. IF DAMAGED, THE RCM MUST BE REPLACED WHETHER OR NOT THE AIR BAGS HAVE DEPLOYED. IN ADDITION, MAKE SURE THE AREA OF THE RCM MOUNTING IS RESTORED TO ITS ORIGINAL CONDITION.

For this vehicle the SRS employs two impact sensors. One of the sensors is integral to the RCM and is not separately serviceable. A front impact severity sensor is located in the front center of the vehicle, behind the grille. The RCM is mounted on the center tunnel under the instrument panel. Mounting orientation is critical for correct operation of all impact sensors.