Air Bag and Safety Belt Pretensioner Supplemental Restraint System (SRS) Components
Air Bag and Safety Belt Pretensioner Supplemental Restraint System (SRS)
The air bag and safety belt pretensioner supplemental restraint system (SRS) is designed to provide increased collision protection for front seat occupants in addition to that provided by the three-point safety belt system. Safety belt use is necessary to obtain the best occupant protection and to receive the full advantages of the SRS.
The air bag and safety belt pretensioner supplemental restraint system (SRS) components are shown in the following illustration.
Air Bag and Safety Belt Pretensioner Supplemental Restraint System (SRS) Components
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 one of two different rates depending upon crash severity, safety belt usage, and driver seat position.
- will deploy upon receiving a signal from the restraints control module (RCM).
- has no subassemblies.
Clockspring
The clockspring:
- is mounted on the steering column, behind the steering wheel.
- continuously transfers electrical signals from the restraints control module (RCM) to the driver air bag module.
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 supplemental restraint system (SRS).
NOTE: For additional information, when servicing a seat equipped with a side air bag module. Service and Repair
The driver side air bag module:
- will deploy upon receiving a signal from the restraints control module (RCM) initiated by the driver side impact sensor.
- is installed as an assembly.
- is mounted in the driver seat back.
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 supplemental restraint system (SRS).
The passenger air bag module:
- is a dual-stage air bag, deploying at one of two different rates depending upon crash severity and safety belt usage.
- will deploy upon receiving a signal from the restraints control module (RCM).
- is installed as an assembly.
- is mounted in the passenger 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 supplemental restraint system (SRS).
NOTE: For additional information, when servicing a seat equipped with a side air bag module. Service and Repair
The passenger side air bag module:
- will deploy upon receiving a signal from the restraints control module (RCM) initiated by the passenger side impact sensor.
- is installed as an assembly.
- is mounted in the passenger seat back.
Safety Belt Pretensioners
As part of the supplemental restraint system (SRS), the safety belt buckles are equipped with pretensioners. The safety belt buckle pretensioners remove excess slack from the safety belt webbing. The pretensioners are activated by the restraints control module (RCM) when the module detects a crash event force exceeding a programmed limit.
Safety Belt Switches
As part of the supplemental restraint system (SRS), the safety belt buckles are equipped with switches. The safety belt switches indicate to the restraints control module (RCM) whether the safety belts are connected (switch closed) or disconnected (switch open). The RCM uses this information in determining the deployment rate of the dual-stage driver and passenger air bag modules.
Seat Track Position Sensor
NOTE: The seat track position sensor on a power seat is serviced as an assembly with the power seat track.
The seat track position sensor informs the restraints control module (RCM) of the drivers 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 restraints control module (RCM) is mounted on the center tunnel under the instrument panel. The RCM performs the following functions:
- signals the inflators to deploy the air bags in the event of a deployable crash.
- activates the safety belt buckle pretensioners to remove slack from the safety belt webbing.
- monitors the air bag supplemental restraint system (SRS) for faults.
- illuminates the air bag indicator if a fault is detected.
- flashes the air bag indicator to indicate the lamp fault code (LFC) detected.
- communicates through the data link connector (DLC) the current or historical diagnostic trouble codes (DTCs).
- signals the generic electronic module (GEM) to activate a chime if the air bag indicator is not available and another SRS fault exists.
- contains an internal safing sensor which is not serviced separately.
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 air bag indicator located in the instrument cluster.
When the ignition is cycled (turned off and then on), the air bag indicator will remain lit for six seconds and then go out. If an SRS fault exists, the air bag indicator will then flash the two-digit lamp fault code (LFC) associated with that fault. The air bag indicator will flash the LFC five times, then remain illuminated for the rest of the key cycle. The RCM will also communicate the current and historical diagnostic trouble codes (DTCs) through the data link connector (DLC) using a scan tool. If the air bag indicator does not function, and the system detects a fault condition, the RCM will signal the generic electronic module (GEM) to activate an audible chime. The chime is a series of five sets of five tone bursts. If the chime is heard, the SRS and the air bag indicator require repair.
LFCs are prioritized. If two 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 backup power to deploy the air bags and the safety belt pretensioners in the event that the ignition circuit is damaged in a collision before the safing and air bag sensors determine that an air bag deployment is required. The backup power supply will deplete its stored energy approximately one minute after the battery ground cable is disconnected.
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 restraints control module (RCM) to the SRS components.
- provides the electrical path from the RCM to the air bag indicator.
- provides the electrical path from the RCM to the data link connector (DLC).
- provides the electrical path from the RCM to the generic electronic module (GEM).
Impact Sensors
WARNING: Mounting orientation of the impact sensors and the RCM is critical for proper 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, the RCM and sensors must be replaced 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.
The impact sensors provide data to the RCM for use in calculating impact severity. This is accomplished using various electrical and electro-mechanical sensors located throughout the vehicle. A front impact severity sensor is located in the front-center of the vehicle, behind the grille. In addition on vehicles equipped with seat side air bags, there are side impact sensors located near the base of each B-pillar.