Data Extraction Methods and their Effects on the Retention of Event Data Contained in the Electronic Control Modules of Detroit Diesel and Mercedes-Benz Engines

The Electronic Control Modules (ECMs) aboard many on-highway commercial motor vehicles contain event data useful to the investigation and reconstruction of motor vehicle collisions [1,2,3,4]. Methods of extracting such event data include: connecting to the ECMs through the vehicle's Off-Board Diagnostics Connector (a 6 or 9 pin connector typically found inside the vehicle near the driver's seat); connecting directly to any ECMs while they are still connected to the engine; and connecting directly to the ECMs after they are removed from the engine (a method typically referred to as a Bench image). This research is an attempt to document the effects of these data-extraction methods on the retention of the event data contained in the ECMs of the on-highway commercial motor vehicle engines manufactured by Detroit Diesel and Mercedes-Benz. In particular, the different data extraction methods listed above were compared to determine what effect, if any, the methodologies had on the preservation of ECM event data. The testing showed that the Last Stop Record and Hard Brake event data were not affected by data-extraction methodology, whereas Diagnostic Records produced as a result of fault codes could be affected by data extraction methodology.