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 - The event can occur at any time. There is no defined time or interval for the event to occur within. This represents the battery voltage available at the time of the indicated measurement. With the ignition switch in the RUN position and the engine not running, the voltage will likely be between 11.5 and 12.5 volts At engine idle, the voltage may be 14 to 16 volts. The voltage could be as low as 10 volts during engine cranking.

BULB TEST - The inflatable restraint Sensing and Diagnostic Module (SDM) will cause the AIR BAG warning lamp to flash seven times. Under normal operation this occurs when the ignition switch transitions from the OFF position to the RUN position. The bulb test will also occur if IGNITION 1 voltage exceeds 17.1 volts and then returns to the normal operating voltage range. The presence of a malfunction could prevent the SDM from flashing the warning lamp.

CONTINUOUS MONITORING TEST - Tests performed by the inflatable restraint Sensing and Diagnostic Module (SDM) on the SIR system during each 100 millisecond interval. The IGNITION 1 voltage at the SDM must be within the normal operating voltage range for continuous monitoring to occur. These tests follow the POWER-ON tests.

DATA LINK CONNECTOR (DLC) - The DLC connects to multiple on-board computers using wires. The DLC allows 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 of the vehicle. All vertical measurements originate from this base line.

DEPLOY - To inflate the air bag.

DEPLOYMENT LOOP CONTINUITY TEST - Tests performed by the inflatable restraint Sensing and Diagnostic Module (SDM) that check voltage differences between the DRIVER SIDE HIGH and LOW and PASS SIDE HIGH and LOW circuits. First the SDM measures IGNITION 1 and 23 VLR in order to verify them to be within their respective normal voltage ranges. Then the SDM 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 current to the inflator modules to deploy the air bags.

DIAGNOSTIC TROUBLE CODE (DTC) - An alphanumeric designator used by the inflatable restraint Sensing and Diagnostic Module (SDM) to indicate specific SIR system malfunctions.

DRIVER CURRENT SINK - An output of the inflatable restraint Sensing and Diagnostic Module (SDM) that supplies a low resistance path to ground for the inflatable restraint steering wheel module circuit.

DRIVER CURRENT SOURCE - An output of the inflatable restraint Sensing and Diagnostic Module (SDM) that supplies current to the inflatable restraint steering wheel module circuit.

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 diagnostic trouble code 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 criticality of the malfunction with respect to deployment or non-deployment under any given condition.

IGNITION CYCLE - An event caused by the operation of the ignition switch. First the inflatable restraint Sensing and Diagnostic Module (SDM) must sense IGNITION 1 input greater than 8.2 volts with the ignition switch in the RUN position. Then this IGNITION 1 input must remain above 8.2 volts for at least 10 seconds before turning the ignition switch to the OFF position.

IGNITION 1 - A battery voltage (B+) circuit receiving power with the ignition switch in the RUN, or START positions.

INFLATABLE RESTRAINT SENSING AND DIAGNOSTIC MODULE -The Sensing and Diagnostic Module (SDM) that provides reserve energy to the deployment loops, deploys the air bags when required and performs diagnostic monitoring of all the SIR system components.

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.

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

INFLATABLE RESTRAINT I/P MODULE ENABLE SWITCH - A manual two-position key switch located in the instrument panel, to the right of the steering wheel. This switch gives the vehicle operator the ability to enable or disable inflatable restraint I/P module (Passenger Front Air Bag) deployment should the vehicle be involved in a severe frontal collision. The vehicle operator may choose to disable the inflatable restraint I/P module if there is no occupant in the front seat, or if there is a child in a rear-facing child seat in the front seat.

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 2 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 - The electrical component inside the inflator module. This component sets off the chemical reaction that inflates the air bag. This chemical reaction occurs when sufficient current flows through this component.

NORMAL OPERATING VOLTAGE RANGE - The voltage measured between the inflatable restraint Sensing and Diagnostic Module (SDM) IGNITION 1 terminal and Ground terminal is between 8.2 and 17.1 volts.

PASSENGER CURRENT SINK - An output of the inflatable restraint Sensing and Diagnostic Module (SDM) that supplies a low resistance path to ground for the inflatable restraint I/P module circuit.

PASSENGER CURRENT SOURCE - An output of the inflatable restraint Sensing and Diagnostic Module (SDM) that supplies current to the inflatable restraint I/P module circuit.

POWER-ON TEST - Tests that the inflatable restraint Sensing and Diagnostic Module (SDM) performs on the SIR system once during each ignition cycle. These tests occur immediately after the SDM receives IGNITION 1 voltage. These tests occur before the CONTINUOUS MONITORING tests.

RESISTANCE MEASUREMENT TEST - Test performed by the inflatable restraint Sensing and Diagnostic Module (SDM) once during each ignition cycle to measure the resistance of the deployment loops. First the SDM measures IGNITION 1, 23 VLR, and the deployment loop voltages in order to verify them to be within their respective normal voltage ranges. Then the SDM sources a constant current to the deployment loop. The SDM then measures the voltage drop across the deployment loop. The SDM converts the measured voltage value to a resistance value. This resistance value is within the range of 0 - 6.3 ohms. Upon the detection of an open circuit, the SDM aborts the tests. This will prevent the calculation of the resistances until the next ignition cycle. This test also checks for proper operation of the driver and passenger current sources. This test is part of the POWER-ON tests and occurs before the CONTINUOUS MONITORING tests.

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

SERIAL DATA - The information communicated to an off-board computer using the data link connector. Some of this information represents the status of the SIR system.

SIR - Supplemental Inflatable Restraint.

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

23 VLR - The 23 Volt Loop Reserve. This is an energy supply internal to the inflatable restraint Sensing and Diagnostic Module.