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:

- LH and RH front impact severity sensor
- Driver and passenger side impact sensor
- Safety belt buckle switches
- Driver seat track position sensor
- Occupant Classification System Module (OCSM)

If the RCM detects sudden vehicle deceleration and/or lateral deceleration based on the information received from sensors and switches and determines that deployment is required, the RCM sends voltage and current to deploy the appropriate SRS components.

During a frontal or side crash, the RCM may deploy the following SRS components, based on crash severity and sensor input.

- Safety belt retractor pretensioner(s)
- Seat side air bag(s)
- Driver/passenger dual-stage air bag (one or both stages)

The fact that the 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 performs a self-test of the complete SRS during each startup. If a SRS 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 continuously monitors all SRS components and circuitry for correct operation.


Air Bag Warning Indicator

The air bag warning indicator:

- located in the Instrument Cluster (IC) module, will prove out by lighting for 6 seconds and then turn off.
- will flash and/or illuminate based on the message the IC module receives from the RCM.
- will illuminate if the IC module does not receive a message from the RCM.

Air Bag Module Second Stage Deployment Check

Because the driver and passenger front air bags each have 2 deployment stages, it is possible that stage 1 has deployed and stage 2 has not.

If a front air bag module has deployed, it is mandatory that the front air bag module be remotely deployed using the appropriate air bag disposal procedure.

- For information on driver air bag module and/or passenger air bag module remote deployment, refer to Pyrotechnic Device Disposal Service and Repair.


Clockspring

The clockspring allows for continuous electrical connections between the driver air bag module and the RCM when the steering wheel is turned.


Driver Air Bag Module

The driver air bag module is a dual-stage air bag, upon receiving a flow of current from the RCM, deploying at 1 of 2 different rates depending upon vehicle impact severity and sensor input.