Crash pulse:  Relates to the acceleration change the airbag SDM 'sees' during an accident event.

CDR:  Related to the Vetronix Bosch CDR module. Aka the 'Crash Data Retrieval' tool. Also incorrectly called crash data recorder.

Continuous Monitoring Test:  The SDM module continuosly moniters the SIR system during each 100 millisecond interval.

CPA:  Connector position assurance.

Data Link Connector:  The DLC electronically connects to many on-board computers and also with scan tools. AKA as the ALDL or Assembly Line Diagnostic Link. OBDI, OBDII connector.

Datum Line:  A base line parallel to the plane of the vehicle.

Deploy:  To inflate the air bag.

Deployment Loop Continuity Test:  SDM test of the drivers and passenger airbag circuitry.

Deployment Loops:  The circuits that provide the current to the inflator modules for air bag deployment.

DERM:  Diagnostic Energy Reserve Module. Older GM term for the airbag module. See 'SDM.'

Diagnostic Trouble Codes (DTC):  A set of codes used by the SDM in order to indicate specific SIR system malfunctions.

EDR / Event data recorder: Technically called the air bag SDM module on GM vehicles. Generic industry term for the 'black box' data. Also called crash data recorders or EDR.  

EEPROM:  Electrically Erasable Programmable Read Only Memory.

Event:  Accident, collision, crash, impact, wreck, rollover, rearended, side impact, etc.

Ignition Cycle:  The ignition switch causes this cycle to occur. The SDM counts how many ignition cycles have occured before a crash event.

EFS:  Inflatable Restraint Front End Discrimating Sensor / A sensor mounted on the front of the vehicle that supplies an input signal to the SDM.

GM advanced air bags:  Newer crash and deployment system. More info can be found at this link. http://www.freep.com/money/autonews/airbags9e_20050209.htm Many early OnStar systems will no longer be functional after 01/01/2008 due to FCC regulations concerning Analog phone systems. Most 2002 and newer GM vehicles can be upgraded to digital service. Most 2001 and older GM vehicles will not be upgradeable. This FCC regulation also effects Lexus, Infiniti, Mercedes Benz vehicle systems.


Inflatable Restraint I/P module:  Passenger side airbag, an inflater, and an initiator.

Inflatable Restraint Steering Wheel Module:  Drivers side airbag, an inflater, and an initiator.

PPS / passenger presence systems:  FMVSS (Federal Motor Vehicle Safety Standards) requires all vehicles sold in the U.S. to be equipped with automatic passenger airbag suppression by model year 2006. The PPS monitors the occupant on the front outboard passenger seat and communicates the status to the sensing and diagnostic module (SDM) whether to enable or suppress the deployment of the I/P module.

Steering Wheel Module Coil:  Like a clockspring. The assembly allows the rotation of the steering wheel while maintaining continuous electrical circuit contact with the air bag and some steering wheel controls.

Steering Column:  The steering column is energy absorbing. It can compress during a frontal crash to decrease the chance of injury to the driver.

Initiator:  The initiator initiates the chemical reaction that inflates the air bag.

OBD: On Board Diagnostics. There are really 2 different systems currently on roads. OBDI, which is version 1. And OBDII, which is 'on board diagnostics version 2.' OBDII is typically 1996 and newer vehicles. Some 1994-1996 GM vehicles are OBDII.

RCM:  Ford version of an air bag module.

SDM:  GM Inflatable Restraint Sensing and Diagnostic air bag Module. Aka the 'black box' or EDR. SDM is the newer GM term for the airbag module. See 'Derm.' The SDM moniters the side impact module if equipped. The SDM records information during a crash event.

SISM: / aka SIS  Inflatable Restraint Side Impact Sensing (and Diagnostic) Module. If equipped. Side impact crash detection.

Knee Bolster:  Knee bolsters absorb energy and control forward movement of the front seat occupants during a frontal crash.

Normal Operating Voltage Range:  Depending on year. 8.2-17.1 VDC or 7.8-18.0 VDC.

OnStar:  Current GM onboard subscription communications device. Technically a car based analog cell phone. Future versions will have both analog and digital coverage. Onstar will attempt to call you if there is a deployment or near deployment event, typically about 15-20 seconds after the deployment event or near deployment event. See 'Advanced Automatic Crash Notification.' * Many early OnStar systems will no longer be functional after 01/01/2008 due to FCC regulations concerning Analog phone systems. Most 2002 and newer GM vehicles can be upgraded to digital service. Most 2001 and older GM vehicles will not be upgradeable. This FCC regulation also effects Lexus, Infiniti, Mercedes Benz vehicle systems.

Power-on Test:  A test the SDM performs once per ignition cycle in order to measure the resistance of the deployment loops.

Scan Tool:  An off-board computer that reads on-board computer diagnostic information via the DLC/ALDL. GM Tech 1a, GM Tech 2, Snap-on, OTC are all examples of diagnostic scan tools.

Serial Data:  The information communicated to an off-board computer using the DLC/ALDL. See Tech 2 scanner.

SIR:  Supplemental inflatable restraint.

SRS:  Supplemental restraint system.

State Of Health (SOH) DTCs:  Diagnostic trouble codes set by any module communicating on the Serial Data Line Class 2.

23 VLR:  The 23 volt loop reserve. The energy supply that is internal to the SDM.

GM Tech 2:  Current GM factory/dealer diagnostic scanner tool. See 'scan tool.' The GM Tech 2 cannot collect the air bag crash data from the GM air bag SDM.

Seat Belt Pretensioners:  During a crash event the SDM can ignite the material in the pretensioner gas generator. This reaction rapidly shortens the seat belt buckle height. They must be replaced after a deployment event.