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

AIR BAG AND SAFETY BELT PRETENSIONER SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

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 3-point safety belt system. The SRS will also provide increased collision protection for the rear occupants when equipped with optional safety canopy modules. Safety belt use is necessary to obtain the best occupant protection and to receive the full advantage of the SRS.

This vehicle line contains dual-stage deployment (advanced restraint system) driver and front passenger air bag modules. These vehicles are also equipped with optional safety canopy modules.

Vehicles equipped with safety canopy modules are also equipped with seat side air bag modules. Safety canopy modules deploy from the headliner, protecting the first and second row outboard occupants (Five Hundred and Montego) or first, second and third row outboard occupants (Freestyle) during a side impact or if a rollover condition is detected. Seat side air bag modules deploy from the outboard front seat backrest upon a side impact.

Before servicing the SRS, the system must be depowered.

Air Bag And Safety Belt Pretensioner Supplemental Restraint System (SRS) Components - (Illustration 1 Of 2):

Air Bag And Safety Belt Pretensioner Supplemental Restraint System (SRS) Components - (Illustration 2 Of 2) (Part 1):

Air Bag And Safety Belt Pretensioner Supplemental Restraint System (SRS) Components - (Illustration 2 Of 2) (Part 2):

Air Bag And Safety Belt Pretensioner Supplemental Restraint System (SRS) Components - (Illustration 1 Of 2) (Part 1):

Air Bag And Safety Belt Pretensioner Supplemental Restraint System (SRS) Components - (Illustration 1 Of 2) (Part 2):

Air Bag And Safety Belt Pretensioner Supplemental Restraint System (SRS) Components - (Illustration 2 Of 2) (Part 1):

Air Bag And Safety Belt Pretensioner Supplemental Restraint System (SRS) Components - (Illustration 2 Of 2) (Part 2):

Clockspring
The clockspring:
- is mounted on the steering column, behind the steering wheel.
- allows continuous electrical contact between the RCM and the driver air bag module when the steering wheel is turned.

Driver Air Bag Module

NOTE: References to the driver air bag module must not be confused with the side (seat-mounted) air bag components of the supplemental restraint system (SRS).

The driver air bag module:
- is steering-wheel mounted.
- is a dual-stage air bag, deploying at 1 of 2 different rates depending upon impact severity, safety belt usage and driver seat position.
- will deploy upon receiving a flow of current from the restraints control module (RCM).
- has no subassemblies.

Deployable Steering Column

NOTE: If the deployable steering column electrical connector becomes damaged or the deployable steering column has deployed, a new overlay wiring harness must be installed. Make sure to follow the installation instructions that are included in the service kit.

This vehicle is equipped with a deployable steering column. The deployable steering column includes a deployable device that, once deployed, reduces the amount of force necessary to collapse the steering column during a crash event. The deployable device is activated by the restraints control module (RCM) depending on when the module detects a crash event force exceeding a programmed limit and the position of the driver seat. After deployment, a new steering column must be installed.

Driver Seat Side Air Bag Module

NOTE: References to side air bag modules refer to the seat-mounted and not to the steering wheel or instrument panel mounted air bag components of the SRS.

The driver seat side air bag module:
- will deploy upon receiving a flow of current from the RCM initiated by the driver seat side impact sensor and internal RCM circuitry.
- is installed as an assembly.
- is mounted in the driver seat back.

Electrical System
The electrical system that supports the air bag supplemental restraint system (SRS):
- is powered from the battery through the ignition circuit.
- provides the electrical path from the RCM to the SRS components.
- provides the electrical path from the RCM to the restraints indicator lamp.
- provides the electrical path from the RCM to the data link connector (DLC).
- provides the electrical path from the RCM to the instrument cluster module.

High Speed Controller Area Network (HS-CAN)
This vehicle utilizes a communication system called a high-speed controller area network (HS-CAN). The HS-CAN consists of a twisted pair of wires connected to the following:
- Anti-lock brake system (ABS) module
- Instrument cluster module
- Occupant classification sensor (OCS) system
- Powertrain control module (PCM)
- Transmission control module (TCM)
- Restraints control module (RCM)
- Data link connector (DLC)

The HS-CAN circuits use a bias voltage of approximately 2.5 volts, one is a positive 2.5 volts while the other is a negative 2.5 volts. The HS-CAN also uses 2 terminating resistors, one contained within the PCM, the other in the instrument cluster module. The terminating resistors are not serviced separately. The terminating resistors have a value of 120 ohms each, for a total normal operating system total of 60 ohms. The HS-CAN will operate with only one terminating resistor and has the capability to communicate some messages to some of the control modules with only one circuit functioning, but at a reduced rate of performance.

Impact Sensors

WARNING:
- Mounting orientation of the impact sensors and the RCM is critical for correct system operation. If a vehicle has been involved in a collision in which the center tunnel area has been damaged, inspect the RCM mounting area for deformation. Inspect the impact sensor mounting area for damage. If damaged, a new RCM and sensors must be installed whether or not the air bags have deployed. In addition, make sure the mounting area of the RCM and impact sensors are restored to the original production configuration.
- Vehicle sensor orientation is critical for correct system operation. If a vehicle equipped with an air bag supplemental restraint system (SRS) is involved in a collision, inspect the sensor mounting bracket and wiring pigtail for deformation. Install and correctly position a new sensor or any other damaged supplemental restraint system (SRS) components whether or not the air bag is deployed.

The impact sensors provide data to the RCM for use in calculating impact severity. This is accomplished using various electrical sensors located throughout the vehicle.

For these vehicles, the SRS employs up to 7 impact sensors. One of the sensors is integral to the RCM and is not separately serviceable. The RCM 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, on vehicles equipped with seat side air bags and safety canopies, there are 4 side impact sensors located on or near the base of each B- and C-pillar. Mounting orientation is critical for correct operation of all impact sensors.

Occupant Classification Sensor

CAUTION:
- It is necessary to rezero the OCS system when a front passenger seat cushion is disassembled, a new trim cover installed, or an OCS service kit is installed. A diagnostic tool is used to trigger the active command to carry out rezeroing of the OCS system.
- Make sure the seat is completely assembled before rezeroing.

NOTE: To identify between a production OCS system and a service OCS system (OCS service kit), inspect the electronic control unit (ECU) electrical connector. A production OCS system allows the disconnection of the ECU electrical connector. A service OCS system (OCS service kit) has the ECU electrical connector glued to the ECU, it cannot and should not be disconnected or altered. An OCS system service kit also has an in-line connector between the OCS ECU and the seat wiring harness.

The seat occupant classification sensor (OCS) system is found only on the front passenger seat. The front passenger seat OCS system 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 system 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 system pressure sensor, then electronically communicated to the OCS system electronic control unit (ECU). Based on preprogrammed set points, the OCS system ECU will inform the restraints control module (RCM), via a high-speed controller area network (HS-CAN), of the necessary information. The RCM uses this information in determining if the passenger air bag module is to be deployed in the event of a deployable collision. The RCM may also use this information to illuminate/not illuminate the passenger air bag deactivation (PAD) indicator.

When an OCS system fault is present, the air bag indicator lamp will illuminate or the air bag warning chime will be activated (if an air bag indicator fault is present). The SRS then defaults the passenger air bag module to ON (activated) regardless of the size of the occupant in the front outboard passenger seat.

The OCS system components (seat cushion foam pad, bladder with pressure sensor and electronic control unit) are calibrated to each other and are serviced as an assembly. OCS system components are not to be installed separately. If installing a new OCS system, OCS system component or seat cushion foam pad, a new OCS system service kit (seat cushion foam pad, bladder with pressure sensor and electronic control unit) must be installed as an assembly.

The OCS system also interprets a variable voltage signal provided by the safety belt tension sensor to identify the presence of a properly fastened child safety seat in the front outboard passenger seat. The OCS system then communicates with the restraints control module (RCM), automatically deactivating the passenger air bag module. Refer to Safety Belt Tension Sensor.

The OCS system is also used for operation of the passenger Belt Minder. To deactivate or reactivate the passenger Belt Minder feature, refer to Seat Belt Systems or the owner literature.

Passenger Air Bag Module

NOTE: References to the passenger air bag module must not be confused with the side (seat-mounted) air bag components of the SRS.

The passenger air bag module:
- is a dual-stage air bag, deploying at 1 of 2 different rates depending upon impact severity and safety belt usage.
- will deploy upon receiving a flow of current from the RCM.
- is installed as an assembly.
- is mounted in the right side of the instrument panel.

Passenger Seat Side Air Bag Module

NOTE: References to side air bag modules refer to the seat-mounted and not to the steering wheel or instrument panel mounted air bag components of the SRS.

The passenger side air bag module:
- will deploy upon receiving a flow of current from the RCM initiated by the passenger side impact sensor and internal RCM circuitry.
- is installed as an assembly.
- is mounted in the passenger seat back.

Safety Canopy Module

WARNING: Anytime the safety canopy module has deployed, the headliner, and all A-, B-, C- and D-pillar upper trim panels and attaching hardware must be replaced along with any other damaged components and hardware. Failure to do so can result in personal injury in the event of a safety canopy module deployment.

NOTE:
- If the headliner has the word "AIR BAG" embossed on it near each B-pillar, the vehicle is equipped with safety canopy modules.
- Safety canopy modules equipped on Five Hundred and Montego vehicles have a single squib (safety canopy module squib 1 only). Safety canopy modules equipped on Freestyle vehicles have a dual squib (safety canopy module squib 1 and safety canopy module squib 2).

The safety canopy module:
- will deploy upon receiving a flow of current from the restraints control module (RCM) initiated by the side impact sensors and internal RCM circuitry when a side impact or vehicle rollover condition is detected.
- is installed as an assembly.
- is mounted above the headliner.
- attaches from the A-pillar frame to the D-pillar frame (Freestyle).
- attaches from the A-pillar frame to the C-pillar frame (Five Hundred and Montego).
- cannot be interchanged from side to side.

Bridge Resistors

NOTE: Do not deactivate the safety canopy module circuit or seat side air bag module circuit by removing the bridge resistor from the electrical connector.

If the safety canopy or seat side air bag bridge resistor is removed, an open circuit fault will be generated by the restraints control module (RCM).

If a restraint system diagnostic tool is installed at the safety canopy or seat side air bag electrical connector, a low-resistance fault will be generated.

The safety canopy bridge resistor:
- is equipped on vehicles without safety canopy modules.
- must not be removed in the deactivation procedure.
- is mounted behind the headliner near the C-pillar on the LH side (Five Hundred and Montego).
- is mounted behind the headliner near the D-pillar on the LH side (Freestyle).

The seat side air bag bridge resistor:
- is equipped on vehicles without seat side air bag modules.
- must not be removed in the deactivation procedure.
- is mounted under the driver and passenger seat to the seat pan.

Safety Belt Buckle Switch
As part of the supplemental restraint system (SRS), the driver and passenger safety belt buckles are equipped with a Hall-effect switch. The safety belt buckle switches indicate to the restraints control module (RCM) whether the safety belt buckles are buckled or unbuckled.

The RCM uses this information in determining the deployment rate of the dual-stage driver and passenger air bag modules.

The safety belt buckle switches are also used for the driver safety belt warning system and the driver and passenger belt minder.

Safety Belt Pretensioners

NOTE: If a safety belt retractor pretensioner has deployed, a new overlay wiring harness must be installed. Make sure to follow the installation instructions that are included in the service kit.

As part of the SRS, the safety belt retractors are equipped with pretensioners. The pretensioners remove excess slack from the safety belt webbing. The pretensioners are activated by the RCM when the module detects an impact event force exceeding a programmed limit.

Passenger Air Bag Deactivation (PAD) Indicator
The passenger air bag deactivation (PAD) indicator is a visual indicator used to inform the front seat occupants of the passenger air bag deactivation state. The PAD indicator is located in the integrated control panel (ICP) in a position visible to each front seat occupant.

The restraints control module (RCM) controls the state of the PAD indicator through a direct hardwire connection, based on information provided by the occupant classification sensor (OCS) system. The PAD indicator is lit to indicate the passenger air bag module is deactivated (OFF). Some exceptions to this are made in certain scenarios such as 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 indicator is unlit when the passenger air bag module is activated (ON).

When the ignition switch is in the RUN position, the PAD indicator prove-out period is initiated by the RCM. The RCM briefly activates the PAD indicator to prove-out the indicator function and verify to the front occupants proper functional operation of the PAD indicator.

The PAD indicator will illuminate/not illuminate within 1.0±0.5 seconds of a change of state from the OCS system.

When an OCS system fault is present, the SRS defaults the passenger air bag module to ON (activated) regardless of the size of the occupant in the front outboard passenger seat. The PAD indicator will be unlit.

Passenger Air Bag And PAD Indicator Status:

The table indicate the passenger air bag status and the PAD indicator status based on the size of the front outboard passenger occupant.

Safety Belt Tension Sensor
The safety belt tension sensor:
- is part of the front outboard passenger safety belt retractor assembly.
- is located at the safety belt anchor point on the passenger seat.
- is used in conjunction with the occupant classification sensor (OCS) system.
- is a 3-wire Hall-effect sensor that is part of the front passenger safety belt and retractor assembly.

The safety belt tension sensor is used by the OCS system to identify the presence of a child safety seat on the front outboard passenger seat. The safety belt tension sensor senses the tension on the safety belt assembly then provides an output to the OCS system electronic control unit (ECU), indicating that the safety belt assembly is cinched. After sensing the weight applied to the seat by the occupant and using the safety belt tension sensor input, the OCS system determines how the occupant should be classified and communicates this information to the restraints control module (RCM). If the occupant is classified to be a child, the RCM will then automatically deactivate the passenger air bag module.

Seat Track Position Sensor
The seat track position sensor informs the RCM of the driver seat position. The RCM uses this information in determining the deployment rate of the dual-stage driver air bag module.

Restraints Control Module (RCM)

NOTE: Care must be taken when disconnecting and connecting the RCM electrical connectors.

The RCM is mounted on the center tunnel between the front seats. The RCM carries out the following functions:
- Deploys the air bags in the event of a deployable impact
- Deploys the seat side air bags in the event of a deployable impact (if equipped)
- Deploys the safety canopies in the event of a deployable impact (if equipped)
- Activates the safety belt retractor pretensioners to remove slack from the safety belt webbing
- Monitors the SRS for faults
- Requests the instrument cluster module to illuminate the restraints indicator lamp (RIL) if a fault is detected
- Illuminates the passenger air bag deactivation (PAD) indicator when conditions warrant illumination
- Requests the instrument cluster module to flash the restraints indicator lamp to indicate the lamp fault code (LFC) is detected
- Communicates through the data link connector (DLC) the current or historical diagnostic trouble codes (DTCs)
- Signals the instrument cluster module to activate a chime if the restraints indicator lamp is not available and another SRS fault exists
- Records deployable and non-deployable impact data

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 restraints indicator lamp located in the instrument cluster.

When the ignition is cycled (turned OFF and then ON), the restraints indicator lamp will remain lit for 6 seconds and then go out. If an SRS fault exists, the restraints indicator lamp will then flash the 2-digit lamp fault code (LFC) associated with that fault. The restraints indicator lamp will flash the LFC 3 times, then remain illuminated for the rest of the key cycle. The RCM will communicate current and history diagnostic trouble codes (DTCs) through the data link connector (DLC) using a diagnostic tool. If the restraints indicator lamp does not function and the RCM detects a fault condition, the RCM will signal the instrument cluster module to activate an audible chime. The chime is a series of 5 sets of 5 tone bursts. If the chime is heard, the SRS and the restraints indicator lamp requires service.

LFCs are prioritized. If 2 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 power to deploy the front air bags and the safety belt buckle pretensioners in the event that the ignition circuit is damaged in a collision before the air bags are deployed. Once ignition voltage is removed, the backup power supply will deplete its stored energy reserve in approximately one minute. The battery ground cable must be removed before deactivating a SRS.