Principles of Operation

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

Principles of Operation
The Restraints Control Module (RCM) continuously receives/monitors all inputs from the following Supplemental Restraint System (SRS) components.

- LH and RH front impact severity sensor
- Driver and Passenger front door side impact sensor
- Driver and Passenger C-pillar side impact sensor
- Safety belt buckle switches (driver and passenger)
- Driver seat track position sensor
- Occupant Classification System Module (OCSM)
If the RCM (Restraints Control Module) detects sudden vehicle deceleration and/or lateral deceleration based on all the information received from all sensors and switches and determines that deployment is required, the RCM (Restraints Control Module) sends voltage and current to deploy the appropriate SRS (Supplemental Restraint System) components.
During a frontal or side crash, the RCM (Restraints Control Module) may deploy the following SRS (Supplemental Restraint System) components, based on crash severity and sensor input.

- Safety belt retractor pretensioner(s)
- Seat side air bag(s)
- Side air curtain(s)
- Driver/passenger dual-stage air bag (one or both stages)
The fact that the safety belt retractor pretensioners, side air curtains and side air bags did not activate for both front seat occupants in a crash does not mean that something is wrong with the system.
The RCM (Restraints Control Module) performs a self-test of the SRS (Supplemental Restraint System) during each startup. If a SRS (Supplemental Restraint System) fault exists, the air bag warning indicator will illuminate and remain illuminated for the rest of the ignition cycle. In addition to the self-test at start up, the RCM (Restraints Control Module) continuously monitors all of its SRS (Supplemental Restraint System) components and circuitry for correct operation.
Air Bag Warning Indicator
The air bag warning indicator:

- located in the Instrument Panel Cluster (IPC) will prove out by lighting for 6 seconds then turn off.
- will flash and/or illuminate based on the message the IPC (Instrument Panel Cluster) receives from the RCM (Restraints Control Module).
- will illuminate if the IPC (Instrument Panel Cluster) does not receive a message from the RCM (Restraints Control Module).
Air Bag Module Second Stage Deployment Check
Because the driver and passenger front air bags each have 2 deployment stages, it is possible that stage 1 has deployed and stage 2 has not.
If a front air bag module has deployed, it is mandatory that the front air bag module be remotely deployed using the appropriate air bag disposal procedure.

- For information on driver air bag module and/or passenger air bag module remote deployment, refer to Pyrotechnic Device Disposal Service and Repair.
Clockspring
The clockspring allows for continuous electrical connections between the driver air bag module and the RCM (Restraints Control Module) when the steering wheel is turned.
Driver Air Bag Module
The driver air bag module is a dual-stage air bag, deploying at 1 of 2 different rates depending upon impact severity and sensor input.
High Speed Controller Area Network (HS-CAN)
This vehicle utilizes a communication system called a High Speed Controller Area Network (HS-CAN). The RCM (Restraints Control Module) communicates with various modules for required information about the vehicle. for additional information about the HS-CAN (High Speed Controller Area Network).
Impact Sensors
For these vehicles, the SRS (Supplemental Restraint System) employs 7 impact sensors. One of the sensors is integral to the RCM (Restraints Control Module) and is not separately serviceable. The RCM (Restraints Control Module) is mounted on the center tunnel between the front seats. There are 2 front impact severity sensors located in the front-center of the vehicle, behind the grille. In addition, there are 4 side impact sensors. The first row side impact sensors are pressure sensors mounted to each front door behind the trim panel. The second row side sensors are located on or near the base of the C-pillar. Mounting orientation is critical for correct operation of all impact sensors.
The side impact sensors are not interchangeable.
Occupant Classification System (OCS) System
The Occupant Classification System (OCS) system is found only on the front passenger seat. The OCS (Occupant Classification System) system classified the size of the front passenger seat occupant and provides this information to the Restraints Control Module (RCM). The RCM (Restraints Control Module) uses this information (and other inputs) in determining the deployment strategy of the passenger air bag module and pretensioner. The front passenger OCS (Occupant Classification System) system is comprised of the following: 4 OCS (Occupant Classification System) weight sensor bolts that are mounted to each corner of the seat track and an OCSM (Occupant Classification System Module) 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 electronically communicated to the OCSM (Occupant Classification System Module). The OCS (Occupant Classification System) weight sensor bolts are serviced as an assembly (2 weight sensor bolts and mounting bracket per side), the OCSM (Occupant Classification System Module) is serviced separately.
The OCS (Occupant Classification System) system is also used for operation of the passenger Belt-Minder(R). For information on the passenger Belt-Minder(R) feature, refer to Seat Belt Systems. To deactivate or reactivate the passenger Belt-Minder(R) feature, refer to Instrument Panel, Gauges and Warning Indicators or the Owner's Literature.
Passenger Air Bag Deactivation (PAD) Indicator
The RCM (Restraints Control Module) controls the state of the Passenger Air Bag Deactivation (PAD) indicator, based on information provided by the OCS (Occupant Classification System) system. The PAD (Passenger Air Bag Deactivation) indicator is lit to indicate the front passenger air bag module is disabled. An exception 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 cases, the PAD (Passenger Air Bag Deactivation) indicator is off when the passenger air bag module is enabled.
The RCM (Restraints Control Module) briefly activates the PAD (Passenger Air Bag Deactivation) indicator to prove-out the indicator function and verify to the front occupants correct functional operation of the PAD (Passenger Air Bag Deactivation) indicator.
The following table indicates the passenger air bag status and the PAD (Passenger Air Bag Deactivation) indicator status based on the size of the front passenger occupant.

Passenger Air Bag and PAD (Passenger Air Bag Deactivation) Indicator Status





Passenger Air Bag Module
The passenger air bag module is a dual-stage air bag, deploying at 1 of 2 different rates depending upon impact severity, sensor input, safety belt usage and passenger seat occupant classification.
Restraints Control Module (RCM)
WARNING: If a vehicle has been in a crash, inspect the restraints control module (RCM) and the impact sensor (if equipped) mounting areas for deformation. If damaged, restore the mounting areas to the original production configuration. A new RCM and sensors must be installed whether or not the air bags have deployed. Failure to follow these instructions may result in serious personal injury or death in a crash.

NOTE:This vehicle is equipped with the SYNC(R) feature which contains the 911 assist option. Refer to the Owner's Literature.
The RCM (Restraints Control Module) carries out the following functions:

- Deploys the air bag(s)/side air curtain(s) in the event of a deployable collision
- Activates the safety belt retractor pretensioner to control tension on the safety belt in the event of a deployable collision
- Monitors the SRS (Supplemental Restraint System) for faults
- Sends a message to the IPC (Instrument Panel Cluster) to flash/illuminate the air bag warning indicator if a fault is detected
- Communicates through the DLC (Data Link Connector) the current or historical DTCs
The RCM (Restraints Control Module) monitors the SRS (Supplemental Restraint System) for possible faults. If a SRS (Supplemental Restraint System) fault exists, the RCM (Restraints Control Module) sends a message to the IPC (Instrument Panel Cluster) to illuminate the air bag warning indicator.
When the ignition is cycled (OFF and then ON), the IPC (Instrument Panel Cluster) will prove out the air bag warning indicator by lighting for 6 seconds and then turn off. If a fault is detected, the RCM (Restraints Control Module) requests illumination of the air bag warning indicator and will remain illuminated for the rest of the ignition cycle. If the RCM (Restraints Control Module) requests illumination of the air bag warning indicator and the air bag warning indicator does not function, the IPC (Instrument Panel Cluster) will automatically activate an audible chime.
The RCM (Restraints Control Module) 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 power and/or ground has been removed from the RCM (Restraints Control Module).
Event Notification Signal
The purpose of the deployment event notification feature is to provide other vehicle subsystems with information pertaining to restraint system deployment or fuel cutoff status. Signal communication between the RCM (Restraints Control Module) and fuel pump control module allows the PCM to initiate fuel cut-off to disable the fuel system in the event of a crash.
The RCM (Restraints Control Module) does not monitor for any circuit faults and will not set a DTC if a fault occurs.
Safety Belt Retractor Pretensioners
The safety belt retractor pretensioners remove excess slack from the safety belt webbing. The pretensioners are activated by the RCM (Restraints Control Module) when the module detects a crash event force exceeding a programmed limit.
Safety Belt Buckle Switches
Safety belt buckle switches indicate to the RCM (Restraints Control Module) whether the safety belts are buckled or unbuckled. The RCM (Restraints Control Module) uses this information in determining the deployment of the dual-stage driver and passenger air bag modules.
Seat Track Position Sensor
The seat track position sensor indicates to the RCM (Restraints Control Module) the position of the driver seat, forward or rearward. The RCM (Restraints Control Module) uses this information in determining the deployment of the dual-stage driver air bag module.
Secondary Air Bag Warning (Chime)
The secondary air bag warning chime, is an audible chime controlled by the IPC (Instrument Panel Cluster). If the IPC (Instrument Panel Cluster) has detected a fault with the air bag warning indicator, a DTC will be stored in the memory of the IPC (Instrument Panel Cluster). Upon receiving the message from the RCM (Restraints Control Module) that a SRS (Supplemental Restraint System) fault has been detected, the IPC (Instrument Panel Cluster) will sound the secondary air bag warning chime in a pattern of 5 sets of 5 beeps.
Seat Side Air Bag Module
The seat side air bag module:

- will deploy upon receiving a flow of current from the RCM (Restraints Control Module) , initiated by the side impact sensor and internal RCM (Restraints Control Module) circuitry.
- is mounted in the seat backrest.
- is used in conjunction with a side air curtain module.
Side Air Curtain Module
WARNING: Anytime the Safety Canopy(R) or side air curtain module has deployed, a new headliner and new A-, B- and C-pillar upper trim panels and attaching hardware must be installed. Remove any other damaged components and hardware and install new components and hardware as needed. Failure to follow these instructions may result in the Safety Canopy(R) or side air curtain module deploying incorrectly and increases the risk of serious personal injury or death in a crash.
The side air curtain module:

- is mounted above the headliner.
- attaches from the A-pillar frame to the C-pillar frame.
Driver Knee Bolster Air Bag Module (Hybrid Vehicles Only)
The driver knee bolster air bag module is mounted behind the steering column opening trim panel and deploys upon receiving a flow of current from the RCM (Restraints Control Module).