Automotive Engineering

 Automotive Alphabet Soup

Investigating or litigating automotive claims cases, which include the collection and analysis of on-board vehicle data can be a confusing venture owing to the variety of data sources from within the vehicle, and the names that people use to describe those sources. For example, Ford calls its device that controls airbag deployment the RCM – Restraint Control Module – while Chrysler calls their functionally equivalent device the ORC – Occupant Restraint Control. Multiply this difference over the dozens of different automobile manufacturers and the problem is quickly apparent. However, understanding a few basic rules and commonalities should help sort through the “alphabet soup” of automotive forensic technology.

One of the most discussed elements of a forensic investigation relates to the on-board event data recorder (EDR). Thus, EDR becomes the first and perhaps most important acronym. Nearly all modern vehicles are equipped with an EDR; that is the easy part. Where it becomes confusing is identifying the source of that data. Alluded to earlier, the airbag system is the source of much of the event-related data, particularly in passenger vehicles. While it is technically correct, and at times helpful to refer to Chrysler’s ORC or Ford’s RCM, it may be easier, yet just as correct, to refer to any manufacturer’s airbag control module as just that – the ACM.

Accessing the data from an ACM requires special equipment. Fortunately, data recorded by the majority of passenger vehicles can be retrieved (aka, “downloaded” or “imaged”) by a single tool: the Crash Data Retrieval, or CDR, system. Vehicles that utilize the CDR system for data retrieval are said to be “supported vehicles” in that they appear in the list of “supported vehicles” within the CDR program’s vehicle look-up section and can be accessed via our website –

EDRs also exist in large commercial trucks, as well, and in these cases the data source is not the ACM. Rather, it is the ECM – engine control module – that provides the data. Another important distinction between passenger cars and commercial trucks is that the latter are NOT supported by the CDR system. Thus, imaging data from commercial trucks requires hardware and software unique to the engine brand being downloaded. So following the bouncing ball of automotive technology nomenclature, the CDR facilitates retrieval of EDR information from the ACM in passenger vehicles but not the ECM in commercial trucks.

Although each manufacturer very likely calls its EDR something unique to their brand, you do not need to remember the dozens of different names in order to communicate accurately and efficiently with your experts or colleagues if you remember the following, generalized acronyms:

EDR – Event Data Recorder
ACM – Airbag Control Module
CDR – Crash Data Retrieval
ECM – Engine Control Module

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