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 sensors
- Driver and passenger front door side impact sensors
- Driver and passenger second row C-pillar side impact sensors
- Safety belt buckle switches (driver and passenger)
- Driver and passenger seat track position sensors
- Occupant Classification System Module (OCSM)
If the RCM (Restraints Control Module) detects sudden vehicle deceleration and/or lateral deceleration based on information received from 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.
The RCM (Restraints Control Module) contains an internal sensor that detects vehicle rollover angles. If the RCM (Restraints Control Module) determines that a rollover condition exists and deployment is required, the RCM (Restraints Control Module) deploys the applicable 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 (driver only)
- Safety belt adaptive load limiting retractor (front passenger only)
- Safety belt buckle pretensioner(s)
- Safety Canopy(R)
- Seat side air bag(s)
- Driver and passenger dual-stage air bags (one or both stages)
- Deployable steering column
The fact that the safety belt buckle pretensioner(s), safety belt retractor(s) or air bag(s) did not activate for both front seat occupants in a crash does not mean that something is wrong with the SRS (Supplemental Restraint System) system.
The RCM (Restraints Control Module) performs a self-test of the complete 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 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.
Air Bag Warning Indicator
The air bag warning indicator:
- located in the Instrument Panel Cluster (IPC) module, will prove out by lighting for 6 seconds and then turn off.
- will flash and/or illuminate based on the message the IPC (Instrument Panel Cluster) module receives from the RCM (Restraints Control Module).
- will illuminate if the IPC (Instrument Panel Cluster) module does not receive a message from the RCM (Restraints Control Module).
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, upon receiving a flow of current from the RCM (Restraints Control Module), deploying at 1 of 2 different rates depending upon vehicle impact severity and sensor input.
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 the event notification signal circuit for faults and will not set a DTC if a fault occurs.
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 information about the HS-CAN (High Speed Controller Area Network).
Impact Sensors
For this vehicle line, the SRS (Supplemental Restraint System) uses 6 satellite sensors in addition to the RCM (Restraints Control Module). The RCM (Restraints Control Module) is mounted to the center tunnel beneath the console. All vehicles have 2 front impact severity sensors located in the front of the vehicle. The first row impact sensors are mounted to each front door 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.
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 classifies the size of 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 and safety belt pretensioner.
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 Collision Avoidance and Parking Assist Systems or the Owner's Literature.
This vehicle line utilizes 2 different types of OCS (Occupant Classification System) systems based on seating option(s), bladder system or weight sensor bolt system.
Occupant Classification System (OCS) System - Bladder System
The OCS (Occupant Classification System) system is comprised of a silicone gel-filled bladder mounted between the seat cushion foam and pan, a pressure sensor that is mounted to the seat frame and an OCSM (Occupant Classification System Module) which is also mounted to the seat frame. Pressure is applied to the OCS (Occupant Classification System) system bladder when weight of any occupant or object in the front passenger seat is present. The pressure is then transferred through a tube, sensed by the OCS (Occupant Classification System) system pressure sensor, then electronically communicated to the OCSM (Occupant Classification System Module). The components of an OCS (Occupant Classification System) bladder system (bladder, pressure sensor and tube, OCSM (Occupant Classification System Module)) are serviced as an assembly.
Occupant Classification System (OCS) System - Weight Sensor Bolt System
The OCS (Occupant Classification System) system is comprised of 4 OCS (Occupant Classification System) weight sensor bolts that are mounted to each corner of the seat track and serviced as an assembly with the seat track. The OCSM (Occupant Classification System Module) is mounted to the electrical bracket underneath the seat cushion pan and can be serviced separately from the seat track assembly. The weight of any occupant or object on the front passenger seat is electronically communicated to the OCSM (Occupant Classification System Module).
Belt Tension Sensor (BTS)
The Belt Tension Sensor (BTS) :
- is a 3-wire Hall-effect sensor and is part of the front passenger safety belt and retractor assembly.
- is used in conjunction with the OCS (Occupant Classification System) system.
The BTS (Belt Tension Sensor) is used to identify the presence of a child safety seat on the front passenger seat. The BTS (Belt Tension Sensor) senses the tension on the safety belt then provides an output to the OCSM (Occupant Classification System Module), indicating that the safety belt is cinched. After sensing the weight applied to the seat or using BTS (Belt Tension Sensor) input, the OCSM (Occupant Classification System Module) determines how the occupant should be classified and communicates this information to the RCM (Restraints Control Module). If the occupant is classified as a child, the RCM (Restraints Control Module) will then automatically deactivate the passenger air bag module and illuminate the Passenger Air Bag Deactivation (PAD) indicator.
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 illuminated 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 (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 Passenger Air Bag Deactivation (PAD) 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 vehicle impact severity and sensor input.
Restraints Control Module (RCM)
WARNING: Do not handle, move or change the original horizontal mounting position of the restraints control module (RCM) while the RCM is connected and the ignition switch is ON. Failure to follow this instruction may result in the accidental deployment of the Safety Canopy(R) and cause serious personal injury or death.
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)/Safety Canopy(R) in the event of a deployable collision
- Activates the safety belt buckle pretensioners to remove slack from the safety belt in the event of a crash
- Activates the driver safety belt retractor pretensioner to remove slack from the safety belt in the event of a crash
- Activates the front passenger adaptive load limiting retractor to control the tension of the front passenger safety belt in the event of a crash
- Monitors the SRS (Supplemental Restraint System) for faults
- Sends a message to the IPC (Instrument Panel Cluster) module to illuminate the air bag warning indicator if a fault is detected
The RCM (Restraints Control Module) monitors the SRS (Supplemental Restraint System) for possible faults. If a fault is detected, the RCM (Restraints Control Module) will request the IPC (Instrument Panel Cluster) module to illuminate the air bag warning indicator. When the ignition is turned OFF and then ON, the IPC (Instrument Panel Cluster) module will prove out the air bag warning indicator by lighting for 6 seconds. If no faults are detected by the RCM (Restraints Control Module), the IPC (Instrument Panel Cluster) module will turn the air bag warning indicator off and it will remain off. If the RCM (Restraints Control Module) detects a fault, it will send a message to the IPC (Instrument Panel Cluster) module to turn the air bag warning indicator on and it will remain on 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) module 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).
Safety Belt Buckle Pretensioners and Safety Belt Retractor Pretensioners
The safety belt buckle pretensioners (driver and front passenger positions) and safety belt retractor pretensioner (driver position only) 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
The safety belt buckles are comprised of integrated circuits called Hall-effect switches. The safety belt buckle switches indicate to the RCM (Restraints Control Module) whether the safety belts are buckled or unbuckled.
The RCM (Restraints Control Module) also communicates the driver safety belt buckle switch status to the IPC (Instrument Panel Cluster) module, which monitors the information to control the safety belt warning indicator. For information on the safety belt warning indicator, refer to Instrument Panel, Gauges and Warning Indicators.
Safety Belt Adaptive Load Limiting Retractor
The front passenger safety belt retractor is equipped with the adaptive load limiting feature that works in conjunction with the safety belt buckle pretensioner to control the tension of the front passenger safety belt in the event of a crash. The front passenger safety belt retractor is also referred to as the seatbelt load limiter.
Safety Canopy(R) 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 Safety Canopy(R) module:
- is mounted above the headliner.
- attaches from the A-pillar frame to the C-pillar frame.
Seat Side Air Bag Module
The side air bag module:
- will deploy upon receiving a flow of current from the RCM (Restraints Control Module), initiated by the RCM (Restraints Control Module).
- is mounted in the seat backrest.
- is used in conjunction with a Safety Canopy(R) module.
Seat Track Position Sensor
The seat track position sensor indicates to the RCM (Restraints Control Module) the position of the seat, forward or rearward. The RCM (Restraints Control Module) uses this information in determining the deployment rate of the dual-stage driver and passenger air bag modules.
Secondary Air Bag Warning (Chime)
The secondary air bag warning chime is an audible chime located in and controlled by the IPC (Instrument Panel Cluster) module. If a fault is detected with the air bag warning indicator, a DTC will be stored in memory of the IPC (Instrument Panel Cluster) module. 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) module will sound the secondary air bag warning chime in a pattern of 5 sets of 5 beeps.