Air Bag Terminology

Air Bag: An inflatable cloth cushion designed to deploy in certain frontal crashes and side impact crashes. The frontal air bags distribute the impact load more evenly over the occupant's head and torso in order to supplement the safety belt protection. The side impact air bags distribute a side impact load more evenly over the vehicle occupant's body.

Asynchronous: An event that can occur at any time without a warning and without falling within a defined time period.

B+: The battery voltage available at the time of the indicated measurement. With the ignition in RUN and the engine stopped, the voltage is usually 11.5-12.5V. With the engine at idle, the voltage may be 14.0 -16.0V. During engine cranking, the voltage can be as low as 10.0V.

Bulb Test: The Instrument Panel Cluster (IPC) will flash the air bag warning indicator 7 times when the ignition switch is turned from OFF to RUN. The inflatable restraint sensing and diagnostic module (SDM) then commands the IPC to turn the warning indicator OFF through serial data communication. This indicates that there are no malfunctions in the SIR system. If a malfunction is present, the IPC flashes the warning indicator seven times and the SDM then commands the IPC to turn the warning indicator ON.

Continuous Monitoring Test: The inflatable restraint sensing and diagnostic module (SDM) continuously monitors the SIR system during each 100 millisecond interval. The Ignition Positive Voltage voltage at the module must be with the normal operating voltage range for the continuous monitoring to occur These tests follow the power-on tests.

Current Sink: An output in each deployment loop of the inflatable restraint sensing and diagnostic module (SDM) that supplies a low resistance path to ground for the respective deployment loop circuit.

Current Source: An output in each deployment loop of the inflatable restraint sensing and diagnostic module (SDM) that supplies current into the respective deployment loop circuit.

Data Link Connector (DLC): The DLC electrically connects to many on-board computers and allows communication with an off-board computer such as a scan tool.

Datum Line: A base line parallel to the plane of the vehicle underbody or the frame. All vertical measurements originate from this base line.

Deploy: To inflate the air bag or actuate the seat belt pretensioner.

Deployment Loop Continuity Test: The inflatable restraint sensing and diagnostic module (SDM) performs this test in order to inspect for voltage variations in the deployment loop circuitry. The module first measures the Ignition Positive Voltage and the 23 VLR in order to verify that the voltage is within specifications. The module then performs the deployment loop continuity test. Detection of a malfunction during these tests may prevent the resistance measurement test from occurring until the next ignition cycle. This test is part of the power-on tests and occurs before the continuous monitoring tests.

Deployment Loops: The circuits that supply the current to the inflator modules for air bag deployment.

Diagnostic Trouble Code (DTC): An alphanumeric designator used by the inflatable restraint sensing and diagnostic module (SDM) in order to indicate specific SIR system malfunctions.

EEPROM (Electrically Erasable Programmable Read Only Memory): Memory that does not require power to the inflatable restraint sensing and diagnostic module (SDM) in order to retain its contents.

Higher Priority Fault: Each DTC has an assigned priority based on its detectability with other DTCs present. The priority corresponds to the detectability of the malfunction only. This does not relate to the seriousness of the malfunction with respect to deployment or non deployment under any given condition.

Ignition Cycle: The operation of the ignition switch causes this cycle to occur. The inflatable restraint sensing and diagnostic module (SDM) must first sense Ignition Positive Voltage input greater than 7.8V with the ignition switch in RUN. The Ignition a Positive Voltage input voltage must remain above 7.8V for at least 10 seconds before turning the ignition switch to OFF.

Ignition Positive Voltage: A B+ circuit receiving power with the ignition in RUN or START.

Inflatable Restraint Front End Discriminating Sensor: A sensor mounted on the front of the vehicle that supplies an input signal to the inflatable restraint sensing and diagnostic module (SDM).

Inflatable Restraint I/P Module: An assembly located on the RH of the I/P consisting of an inflatable air bag, an inflator, and an initiator.

Inflatable Restraint Sensing and Diagnostic Module: The SDM provides reserve energy to the deployment loops, deploys the air bags when required, and performs diagnostic monitoring of all SIR system components.

Inflatable Restraint Side Impact Inflator Modules: An assembly located in the each front door consisting of an air bag, an inflator and an initiator.

Inflatable Restraint Side Impact Sensing (and Diagnostic) Modules (SISM): The SISMs provide reserve energy to the side impact deployment loops, and deploy their respective side air bag when required. The SISMs perform diagnostic monitoring of the side impact air bag system components and communicate the system status to the inflatable restraint sensing and diagnostic module (SDM). Inflatable Restraint Steering Wheel Module: An assembly located in the steering wheel hub consisting of an inflatable bag, an inflator, and an initiator.

Inflatable Restraint Steering Wheel Module Coil: An assembly of two or more current carrying coils mounted within the steering column hub. The assembly allows the rotation of the steering wheel while maintaining continuous electrical circuit contact. Two of the coils provide continuous contact of the driver deployment loop to the inflatable restraint steering wheel module.

Initiator: Located in the inflator module, the initiator initiates the chemical reaction that inflates the air bag when sufficient current flows through the component.

Normal Operating Voltage Range: 7.8-18.0V when measuring between the inflatable restraint sensing and diagnostic module (SDM) Ignition Positive Voltage terminal and ground.