The supplemental inflatable restraint (SIR) system supplements the protection offered by the
occupant seat belt system. The SIR system has several inflator modules located throughout the
vehicle, i.e. The inflatable restraint steering wheel module, inflatable restraint IP module in
passenger side of dash, and the inflatable restraint side impact module - LF and RT. Each inflator
module has a deployment loop that is controlled by the inflatable restraint Sensing and Diagnostic
Module (SDM), which is mounted inside of the vehicle. The SDM determines the severity of a
collision with the assistance of various sensor inputs. When the SDM detects a collision of sufficient
force, it will process the information provided by the sensors to further support inflator module
deployment. The SDM performs continuous diagnostic monitoring of the SIR system electrical
components. Upon detection of a circuit malfunction, the SDM will set a diagnostic trouble code
(DTC) and inform the driver by commanding the instrument panel cluster (IPC) to turn the AIR BAG
indicator ON. The steering column and knee bolsters are designed to absorb energy and compress
during frontal collisions in order to limit leg movement and decrease the chance of injury to the
driver and front passenger.

A frontal collision of sufficient force will deploy the frontal inflator modules. The SDM contains a
sensing device (accelerometer) that converts vehicle velocity changes to an electrical signal. In
some vehicles, the SDM receives a signal from the electronic frontal sensor (EFS) which can help
determine the severity of some types of frontal collisions. The SDM contains a microprocessor,
which performs calculations using the measured accelerations and compares these calculations to
a value stored in memory. When the generated calculations exceed the stored value, the SDM will
cause current to flow through the frontal deployment loops, deploying the frontal inflator modules.
Once the inflator modules are inflated, they quickly deflate through the air bag vent holes and/or
the bag fabric. After the inflator modules are deployed, the SDM sets a deployment commanded
DTC and then commands the IPC to turn the AIR BAG indicator ON. The SDM, IP module, steering
wheel module, steering wheel module coil and the connecting wires make up the frontal deployment
loops. The SDM continuously monitors the deployment loops for malfunctions and commands the
IPC to turn the AIR BAG indicator ON if a fault is detected.
will system work with car off.
No, i don't think it can. Computer needs to see vehicle speed, rate of deceleration and how the
car was hit and where.
Does it cause the seat belts to lock-up?
No, the airbag system has nothing to do with the seatbelt
locking up.
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Vehicle Airbag Operation And Descriptions