Air Bag Supplemental Restraint System (SRS) Components

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. Safety belt use is necessary to obtain the best occupant protection and to receive the full advantages of the SRS.

Air Bag Supplemental Restraint System (SRS) Components:

The air bag supplemental restraint system (SRS) components are shown in the illustration.

Driver Air Bag Module
The driver air bag module:
- is steering-wheel mounted.
- will deploy upon receiving a flow of current from the restraints control module (RCM).
- has no subassemblies.

Clockspring
The clockspring:
- is mounted on the steering column, behind the steering wheel.
- provides a continuous electrical path from the driver air bag module to the restraints control module (RCM).

Passenger Air Bag Module
The passenger air bag module:
- will deploy upon receiving a flow of current from the RCM.
- is installed as an assembly.
- is mounted in the passenger side of the instrument panel.

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 RCM when the module detects an impact event exceeding a programmed limit and the safety belt is latched (connected).

Restraints Control Module (RCM)

WARNING: The restraints control module (RCM) orientation is critical for correct air bag supplemental restraint system (SRS) operation. If a vehicle equipped with an SRS system has been involved in a collision inspect the RCM mounting area and bracket for deformation. If damaged, the RCM must be replaced whether or not the air bags have deployed. In addition, make sure the mounting area of the RCM is restored to its original condition.

CAUTION: To avoid potential damage to the restraints control module (RCM), make sure the RCM and bracket assembly is secured to the floor pan and the SRS is depowered before either disconnecting or reconnecting the RCM electrical connectors.

NOTE:
- When installing a new restraints control module (RCM), always make sure the correct RCM is being installed. If an incorrect RCM is installed, erroneous DTCs will result.
- The RCM has a protective cover that must be removed prior to removal of the RCM or during diagnostic procedures.

The RCM is attached to a bracket, mounted under the front driver seat. The RCM carries out the following functions:
- supplies current flow to 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.
- 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 (on-demand) or historical (continuous) diagnostic trouble codes (DTCs).
- signals the instrument cluster module 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.
- records deployment event 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 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 6-seconds and then go out. If an SRS fault exists, the air bag indicator will then flash the 2-digit LFC. The air bag indicator will flash the LFC 3 times, then it will remain illuminated for the rest of the key cycle. The RCM will also communicate the current and historical DTCs through the (DLC), using a diagnostic tool. If the air bag indicator does not function, and the system 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 air bag indicator require repair.

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 energy to deploy the front air bags and safety belt buckle pretensioners in the event that the ignition circuit is damaged or lost in a collision before the RCM determines that 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):
- receives power from the battery through the ignition circuit.
- provides the electrical path from the restraints control module (RCM) to the SRS components.
- provides the electrical ground path for the air bag indicator.
- provides the electrical path from the RCM to the data link connector (DLC).
- provides the electrical ground path from the instrument cluster to the RCM.

Impact Sensors

WARNING: Vehicle sensor orientation is critical for proper 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 the sensor or any other damaged supplemental restraint system (SRS) components whether or not the air bag is deployed.

Impact sensors are electronic devices that provide crash severity information to the RCM to assist in deployment determination. All vehicles will have a front impact severity sensor located behind the front radiator grille. The RCM is mounted under the front driver seat. Mounting orientation is critical for correct operation of all impact sensors.