Glossary of Terms and Definitions

Air Bag
An inflatable cloth cushion designed to deploy in certain frontal or side impact 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 ON and the engine stopped, the voltage is usually 11.5-12.5 V. With the engine at idle, the voltage may be 14.0-16.0 V. During engine cranking, the voltage can be as low as 10.0 V.

Bulb Test
The inflatable restraint Sensing and Diagnostic and Seat Belt Pretensioner Module (SDM) will cause the air bag warning indicator to come on steady for 3-4 seconds, then turn OFF. Under normal operation, this occurs when the ignition is turned from OFF to RUN. The bulb test will also occur if the IGNITION voltage exceeds 16.0 V and then returns within the normal operating voltage range. A malfunction could prevent the module from flashing the indicator.

Continuous Monitoring Tests
The inflatable restraint Sensing and Diagnostic Module (SDM) continuously monitors the SIR system during each 100 millisecond interval. The IGNITION voltage at the module must be within 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 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.

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 1 input greater than 9.0 V with the ignition switch in RUN. The IGNITION 1 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 switch in the RUN position.

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 And Seat Belt Pretensioner 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 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
9.0-16.0 V when measuring between the inflatable restraint Sensing and Diagnostic Module (SDM) IGNITION POSITIVE VOLTAGE terminal and ground.

Power-on Tests
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 IGNITION 1 voltage, and before the continuous monitoring tests.

Resistance Measurement Test
A test that the inflatable restraint Sensing and Diagnostic and Seat Belt Pretensioner Module (SDM) performs once per ignition cycle in order to measure the resistance of the deployment loops. The module first measures IGNITION, 28.5 VLR, 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.

Scan Tool
An off-board computer that reads on-board computer diagnostic information through the use of a DLC.

Serial Data
The information communicated to an off-board computer using the DLC. Some of this data 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.

VLR
The 28.5 Volt loop reserve. The energy supply that is internal to the inflatable restraint Sensing and Diagnostic and Seat Belt Pretensioner Module (SDM). The 28.5 VLR provides deployment energy for the frontal air bags only.