SIR System Component Definitions

Air Bag: An inflatable cloth cushion designed to deploy in certain frontal 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 Module (SDM) will cause the air bag warning indicator to flash 7 times. Under normal operation, this occurs when the ignition is turned to the RUN position. The bulb test will also occur if the IGNITION 1 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 Test: The Inflatable Restraint Sensing and Diagnostic Module (SDM) continuously monitors the SIR system during each 60 millisecond interval. The IGNITION 1 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 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.

Deployment Loop Voltage Out Of Range Test: This test is run during power-on and continuous monitoring diagnostics. The Inflatable Restraint Sensing and Diagnostic Module (SDM) performs this test in order to inspect for a short to B+ or a short to ground within the deployment loops. If the SDM detects a short to B+ within a deployment loop, the resistance measurement test for that deployment loop will not be run.

Deployment Loop Resistance Measurement Test: This test is run during power-on and continuous monitoring diagnostics. The Inflatable Restraint Sensing and Diagnostic Module (SDM) performs this test in order to inspect for proper deployment loop resistance. This test is run after the voltage out of range test as long as a short to B+ does not exist within the deployment loops.

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.

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 into 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 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 ON. The IGNITION 1 input voltage must remain above 9.0 V for at least 10 seconds before turning the ignition switch to OFF.

Ignition 1: A B+ circuit receiving power with the ignition in RUN or START.

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 Diagnostic Module: The SDM that provides reserve energy to the deployment loops, deploys the air bags 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 1 terminal and ground.

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 IP Module Circuit.

Passenger Current Source: An output of the Inflatable Restraint Sensing and Diagnostic Module (SDM) that supplies current into the Inflatable Restraint IP Module Circuit.

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 IGNITION 1 voltage, and 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.

23 VLR: The 23 volt loop reserve. The energy supply that is internal to the Inflatable Restraint Sensing and Diagnostic Module (SDM).