Air Bag Terminology

AIR BAG - An inflatable cloth cushion designed to deploy in certain frontal crashes. It supplements the protection offered by the seat belts by distributing the impact load more evenly over the vehicle occupant's head and torso.

ASYNCHRONOUS - Performed in a non-periodic fashion, i.e. no defined time or interval.

B+ - Battery voltage, the voltage available at the battery at the time of the indicated measurement. With the key "ON" and the engine not running, the system voltage will likely be between 12 and 12.5 volts. At idle the voltage may be 14 to 16 volts. The voltage could he as low as 10 volts during engine cranking.

BULB TEST - The Sensing and Diagnostic Module (SDM) will cause the "AIR BAG" warning lamp to flash seven times and then go "OFF" whenever the ignition switch transitions to the RUN position from any other ignition switch position and no malfunctions are detected.

"CONTINUOUS MONITORING"- Tests performed by the SDM on the SIR system every 100 milliseconds while "Ignition 1" voltage is in the normal operating voltage range at the SDM.

"CURRENT SOURCE DIAGNOSTICS" - Tests performed by the SDM after ignition, 36 VLR, and deployment loop voltages are all measured within their respective normal voltage ranges. This test checks for proper resistance of the deployment loops and for proper operation of the driver and passenger current sources. If an open is detected this test is aborted before resistance's are calculated, however, should the open clear, this test will be completed meaning resistance's will be checked.

DATA LINK CONNECTOR (DLC) - connector which is connected by wires to multiple on-board computers allowing communication with an off-board computer, such as a scan tool.

DATUM LINE- A base line parallel to the plane of the underbody or frame from which all vertical measurements originate.

DEPLOY - To inflate the air bag.

DEPLOYMENT LOOPS - The circuits which supply current to the inflator modules to deploy the air bags.

DIAGNOSTIC TROUBLE CODE (DTC) - An alphanumerical designator used by the SDM to indicate specific SIR system malfunctions.

DRIVER CURRENT SOURCE - An output of the SDM which injects current into the driver inflator module circuits.

DRIVER INFLATOR MODULE - An assembly located in the steering wheel hub consisting of an inflatable bag, an inflator and an initiator.

EEPROM - Electrically Erasable Programmable Read Only Memory. Memory which retains its contents when power is removed from the SDM.

HIGHER PRIORITY FAULT - Each diagnostic trouble code is assigned a priority based on the detectability with other DTCs present. The priority corresponds to the detectability of the malfunction ONLY, and does NOT relate to the criticality of the malfunction with respect to deployment or non-deployment under any given condition.

IGNITION CYCLE - The voltage at the SDM "Ignition 1" input, with ignition switch "ON," greater than 6.4 volts for at least ten seconds before turning ignition switch "OFF."

IGNITION 1 - A battery voltage (B+) circuit which is only powered with the ignition switch in the RUN, BULB TEST, or START positions.

INITIATOR - The electrical component inside the inflator module which, when sufficient current flows, sets off the chemical reaction that inflates the air bag.

NORMAL OPERATING VOLTAGE RANGE - The voltage measured between the SDM "Ignition 1" terminal and "Ground" terminal is between 6.4 and 16 volts.

PASSENGER CURRENT SOURCE- An output of the SDM which injects current into the passenger inflator module circuit.

PASSENGER INFLATOR MODULE - An assembly located in the right side of the I/P consisting of an inflatable bag, an inflator and an initiator.

SCAN TOOL - An off-board computer used to read diagnostic information from on-board computers via the data link connector.

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

SERIAL DATA - Information representing the status of the SIR system.

SIR - Supplemental Inflatable Restraint.

SIR COIL ASSEMBLY - An assembly of two current-carrying coils in the driver deployment loop that allows the rotation of the steering wheel while maintaining the continuous contact of the driver deployment loop to the driver inflator module.

SIR WIRING HARNESS - The wires and connectors that electrically connect the components in the SIR system.

"TURN-ON" - Test which the SDM performs on the SIR system once during each ignition cycle immediately after "Ignition 1" voltage is applied to the SDM and before "Continuous Monitoring."

36 VLR - The 36 volt loop reserve energy supply from the SDM which provides deployment power when vehicle voltage is lost in a frontal crash.