Advanced Automatic Crash Notification:  GM's advanced automatic crash notification (AACN) system is available on a dozen new 2005 GM models equipped with OnStar. AACN automatically calls an OnStar advisor if the vehicle in involved in a qualified frontal, rear or side impact crashes, regardless of air bag deployment. 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.

AE:  Algorithm Enable,  also known as SDM airbag module 'wakeup.'

Air Bag:  An inflatable cloth cushion designed to deploy in certain frontal crashes. Also used as side airbags in some cars.

Asynchronous:  An event that can occur at any time without a warning and without falling within a defined time period.

B+:  Battery voltage.

Black Box:  Generic industry term for the event data recorder aka the airbag SDM (GM term) and EDR. Like its counterpart in planes, black boxes in cars record crash data that can be retrieved with the Bosch / Vetronix CDR equipment after an accident event. See 'SDM' and 'EDR.'

Bulb Test:  The SDM will cause the air bag warning indicator to flash 7 times. A malfunction could prevent the module from flashing the indicator.

CAN: Newer GM computer data network system. Controller area network.

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

CDR:  Related to the Bosch / Vetronix  CDR tool. 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. A air bag module self-test. IP lamp will flash 7 times. The GM SDM records how many ignition cycles have occured before and after 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.

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.

NHTSA: Not really a GM term. National Highway Traffic Safety Administration.

NTSB: Not really a GM term. National Transportation Saftey Board.

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 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. SDM is the Gerneral Motors term for the air bag module. Example: There is no such thing as a Toyota SDM.

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:  2nd generation GM factory / dealership diagnostic scanner tool. Current newer generation tool is the GM MDI. 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. The seat belt pretensioners can deploy without frontal air bag deployment. They must be replaced after a deployment event.

The listed SDM air bag information above pertains to General Motors, GM, Cadillac, Oldsmobile, Buick, Pontiac, Chevrolet, Hummer, GMC trucks and Saturn vehicles only. Information on your GM car may be different depending on year and model.

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GM SDM airbag location vehicle list © Information contained on this page courtesy Vetronix Corporation © 2003.  Used with permission.

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