by General Motors. In 1976, General Motors introduced a diagnostic module in a very limited number of vehicles. In 1990, General Motors added the Diag- nostic and Energy Reserve Module (DERM). This module recorded the fol- lowing data:
crash sensing activation
times, time from vehicle impact to deploy- ment, fault codes present at the time of deployment and ignition key cycles at the time of deployment. In 1994, General Motors introduced
the Sensing and Diagnostic Module (SDM) to that year’s production vehicles. This version of the module recorded all of the previous data plus, status of driver’s seat belt switch, maximum Delta-V for a near deployment event, Delta-V vs. time for a deployment event, and time between near deployment and deployment events, if within five seconds. In 1999, the General Motors module
began recording the following data: pas- senger airbag enabled/disabled status, engine speed in one second increments for five seconds prior to impact, vehicle speed in one second increments for five seconds prior to impact, brake status (on/ off) in one second increments for five sec- onds prior to impact and throttle position in one second increments for five seconds
prior to impact. For most passenger ve- hicles manufactured since 1999 and which are equipped with a CDR, the above is available.
Data Retrieval Methods. The “black boxes” are typically found in one of three locations: under the cen- ter console, under the front passenger seat or in the dashboard under the radio or climate controls. There are two ways to access the information: through the ve- hicle diagnostic link connection (DLC) or directly from the module. The DLC requires an intact electrical system and the ability to turn the ignition switch. The airbag module can be directly accessed through the data collector port on its side or by removing it from the vehicle (which can be destructive to the vehicle). Pro- prietary software is required to download and interpret the data.
What Data Can be Recovered. • Vehicle Speed – In five one-second intervals preceding impact.
• Engine Speed – In five one-second intervals preceding impact.
• Throttle Position - In five one-sec- ond intervals preceding impact.
• Brake Status - In five one-second
intervals preceding impact.
• Time from vehicle impact to time of maximum Delta-V.
• Time from vehicle impact to airbag deployment.
• Airbag warning lamp status (on/ off ).
• Maximum Delta-V for near de- ployment.
• Driver’s seatbelt status (on/off). • Passenger’s airbag enabled or dis- abled status (on/off).
• Delta-V vs. time for frontal airbag deployment event.
Use of the Data.
place real world investigation and analytical procedures.
The information available does not re- It can, however,
supplement the information and conclu- sions reached by qualified recon- structionists. The importance of getting to the vehicle in a timely fashion goes without saying. If the airbag did not de- ploy in an accident, the data will not be recorded. If the vehicle is destroyed, or repaired, the data will be lost. To prevent loss of the data, it is incumbent upon the practitioner to take the necessary steps to
(Continued on page 20)
Fall 2003
Trial Reporter
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