Component Definitions

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

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 the ON and the engine stopped, the voltage is usually 11.5-12.5V. With the engine running at idle, the voltage may be 14.0-16.0V. During engine cranking, the voltage can be as low as 10.0V.

Continuous Monitoring Test: The Inflatable Restraint Sensing and Diagnostic Module (SDM) continuously monitors the SIR system during each 100 millisecond interval. The ACCESSORY or IGNITION 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.

Data Link Connector (DLC): The DLC electrically connects to many on-board computers and allows communication with those on-board computers. The DLC also allows flash code diagnostics to be enabled when certain terminals are shorted to ground.

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.

Deployment Loops: The circuits that supply the current to the inflator modules and seat belt pretensioners for 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 a voltage input greater than 9.0 V with the ignition switch in ACC or ON. The input voltage must remain above 9.0 V for at least 10 seconds before turning the ignition switch to OFF.

Ignition: A B+ circuit receiving power with the ignition in ON.

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

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

Inflatable Restraint Side Impact Module: An assembly located in the front seat back near the door consisting of an inflatable bag, an inflator, and an initiator.

Inflatable Restraint Side Impact Sensor (SIS): A crash sensing device used in the detection of side impact collisions.

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: 9.0-16.0V when measuring between the Inflatable Restraint Sensing and Diagnostic Module (SDM) IGNITION terminal and ground.

Power-on Test: Tests that the Inflatable Restraint Sensing and Diagnostic Module (SDM) performs on the SIR system once per ignition cycle. These tests occur immediately after the module receives ACCESSORY or IGNITION voltage, and before the continuous monitoring tests.

Resistance Measurement Test: A test that the Inflatable Restraint Sensing and Diagnostic Module (SDM) performs once per ignition cycle in order to measure the resistance of the deployment loops. The module first measures IGNITION and the deployment loop voltages in order to verify readings within specifications. The module then sources a constant current into the loop. The module measures the voltage drop across the loop and converts the value to a resistance value. This resistance value is within the range of 0.0-6.6 ohms. Upon the detection of an open circuit, the module aborts the tests in order to prevent the calculation of the resistances until the next ignition cycle. This test also checks for proper operation of the driver/passenger current sources. This test is part of the power-on tests and occurs before the continuous monitoring tests. Seat Belt Pretensioner: A device mounted in the front seat belt retractors which will rapidly shorten the seat belt height in the event of a mild-to-severe frontal collision.

SIR: Supplemental Inflatable Restraint.

SIR Wiring Harness: The wires and connectors that electrically connect the components in the SIR system.

VLR: The 12-16 volt loop reserve. The energy supply that is internal to the Inflatable Restraint Sensing and Diagnostic Module (SDM). The 12-16 VLR provides deployment energy for the frontal air bags only.