Principles of Operation

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

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

- Front impact severity sensor
- Driver safety belt buckle switch
- Passenger Air Bag Deactivation (PAD) switch
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 crash, the RCM (Restraints Control Module) may deploy the following SRS (Supplemental Restraint System) components, based on crash severity and sensor input.

- Safety belt buckle pretensioner(s)
- Driver and passenger single-stage air bags
The fact that the safety belt buckle pretensioners or 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 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 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 single stage air bag and will deploy depending on vehicle 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 information about the HS-CAN (High Speed Controller Area Network).

Passenger Air Bag Module
The passenger air bag module:

- is a single stage air bag and will deploy depending on vehicle impact severity and sensor input.

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 supports the 911 assist option. Refer to the Owner's Literature.
The RCM (Restraints Control Module) carries out the following functions:

- Activates the driver/passenger air bag modules depending upon vehicle impact severity and sensor input, 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 deployable collision
- Monitors the SRS (Supplemental Restraint System) for faults
- Sends a message to the Instrument Panel Cluster (IPC) module to illuminate the air bag warning indicator if a fault is detected
- Communicates through the Data Link Connector (DLC) the current and/or historical DTCs

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 key 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 chime is a series of 5 sets of 5 tone bursts. If the chime is heard, the SRS (Supplemental Restraint System) and the air bag warning indicator require repair.
The RCM (Restraints Control Module) includes a backup power supply. The backup power supply will deploy the SRS (Supplemental Restraint System) components 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). The backup power supply will deplete its stored energy approximately one minute after the battery ground cable is disconnected.
The RCM (Restraints Control Module) will also communicate the on-demand (current) and continuous (historical) DTCs through the DLC (Data Link Connector) to the scan tool.

Safety Belt Buckle Switches
The driver safety belt buckle is comprised of integrated circuits called a Hall-effect switch. The safety belt buckle switch indicates to the RCM (Restraints Control Module) whether the safety belt 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 Buckle Pretensioners
The safety belt buckle 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.

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 bags 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.

Impact Sensors (Restraints Sensor)
For this vehicle line, the SRS (Supplemental Restraint System) uses one satellite sensor in addition to the RCM (Restraints Control Module). The RCM (Restraints Control Module) is mounted beneath the driver seat. All vehicles have one front impact severity sensor located in the front-center area of the vehicle, behind the grille mounted on the radiator support. Mounting orientation is critical for correct operation of all impact sensors.
The air bag warning indicator may not illuminate to indicate a fault is present until approximately 30 seconds after the ignition switch has been turned from the OFF to the ON position. This is the time required for the RCM (Restraints Control Module) to complete the testing of the SRS (Supplemental Restraint System). If the air bag warning indicator is inoperative and an SRS (Supplemental Restraint System) fault exists, a chime will sound in a pattern of 5 sets of 5 beeps. If this occurs, the air bag warning indicator will need to be repaired before diagnosis can continue.