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:

- Front impact severity sensor

- Driver and passenger front door side impact sensors (if equipped)

- Driver and passenger C-pillar side impact sensors (if equipped)

- Safety belt buckle switch (driver side only)

- Safing and rollover sensors internal to the RCM (Restraints Control Module) (if equipped)

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.

- Driver and passenger safety belt retractor pretensioners

- Driver and passenger single-stage air bags (if equipped)

- Safety Canopy(R) (if equipped)

- Driver and passenger seat side air bags (if equipped)

The fact that the safety belt retractor pretensioner or air bags 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 an SRS (Supplemental Restraint System) fault exists, the air bag warning indicator illuminates and remains 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), proves out by lighting for 6 seconds and then turns off.

- flashes and/or illuminates based on the message the IPC (Instrument Panel Cluster) receives from the RCM (Restraints Control Module).

- illuminates 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, deploying upon receipt of a flow of current from the RCM (Restraints Control Module).

Event Notification Signal (Gas vehicles only)

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 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, the SRS (Supplemental Restraint System) uses as many as 5 satellite sensors in addition to the RCM (Restraints Control Module), depending upon cab configuration. The RCM (Restraints Control Module) is mounted to the center tunnel beneath the floor console or 20 percent seat, depending on seating configuration. All vehicles have 1 front impact severity sensor located in the front of the vehicle. The first row impact sensors (if equipped) are pressure sensors mounted to each front door behind the trim panel. The second row sensors (if equipped, SuperCab and Crew Cab vehicles only) are acceleration-based sensors located on each C-pillar. Mounting orientation is critical for correct operation of all impact sensors.

Vehicles that are not equipped with seat side air bags and the Safety Canopy(R) do not have any side-impact sensors in the front door or C-pillar.

Passenger Air Bag Deactivation (PAD) Switch and Indicator (Regular cab and SuperCab vehicles only)

The Passenger Air Bag Deactivation (PAD) switch allows the passenger air bag deployment circuit to be disabled using the ignition key. The RCM (Restraints Control Module) then controls the state of the PAD (Passenger Air Bag Deactivation) indicator based on information provided by the PAD (Passenger Air Bag Deactivation) switch. The PAD (Passenger Air Bag Deactivation) indicator illuminates to indicate the passenger air bag module is disabled, and 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 correct functional operation of the PAD (Passenger Air Bag Deactivation) indicator.

Passenger Air Bag Module

The passenger air bag module is a single-stage air bag, deploying upon receipt of a flow of current from the RCM (Restraints Control Module).

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.

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 retractor pretensioners to control the tension of the safety belts in the event of a crash

- Monitors the SRS (Supplemental Restraint System) for faults

- Sends a message to the IPC (Instrument Panel Cluster) 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) requests the IPC (Instrument Panel Cluster) to illuminate the air bag warning indicator. When the ignition is turned OFF and then ON, the IPC (Instrument Panel Cluster) proves 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) turns the air bag warning indicator off and it remains off. If the RCM (Restraints Control Module) detects a fault, it sends a message to the IPC (Instrument Panel Cluster) to turn the air bag warning indicator on and it remains 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) automatically activates 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 the ignition circuit is lost or damaged during impact. The backup power supply depletes its stored energy approximately one minute after power and/or ground has been removed from the RCM (Restraints Control Module).

If a new RCM (Restraints Control Module) is installed on vehicles equipped with Roll Stability Control (RSC(R)) or trailer sway control, the IVD initialization sequence must be carried out using the scan tool. Failure to carry out the IVD initialization sequence will result in DTCs being set in the ABS module.

Due to different SRS (Supplemental Restraint System) configurations available for this vehicle, wiring for certain components may be present even though the component is not present. SRS (Supplemental Restraint System) wiring, whether connected to a component or not, should not be used for any other purpose, such as installation of aftermarket accessories. Installing accessories on unused SRS (Supplemental Restraint System) wiring may set RCM (Restraints Control Module) DTCs.

Driver Safety Belt Buckle Switch

The driver safety belt buckle switch indicates 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), 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 Retractor Pretensioner

The safety belt retractor pretensioner removes excess slack from the safety belt webbing. The pretensioner is activated by the RCM (Restraints Control Module) when the module detects a crash event force exceeding a programmed limit.

Safety Canopy(R) Module (if equipped)

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:

- deploys upon receiving a flow of current from the RCM (Restraints Control Module), initiated by the RCM (Restraints Control Module).

- is mounted above the headliner.

- attaches from the A-pillar frame to the B- or C-pillar frame, depending upon cab configuration.

Seat Side Air Bag Module (if equipped)

The side air bag module:

- deploys 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.

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). If a fault is detected with the air bag warning indicator, a DTC is stored in 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) sounds the secondary air bag warning chime in a pattern of 5 sets of 5 beeps.