Since about 1990, all motor vehicles are equipped with Collision Data Recorders (CDR). These devices initially provided impact and status data, as well as deployment commands for occupant protection systems. More recently, vehicles are equipped with drive-by-wire systems with electronically-aided driver controls derived from more than 40 control modules interconnected by communication networks. A vast amount of additional data is collected and stored by these control modules. Diagnostic Trouble Codes (DTCs) identify, describe and store events, faults, limitations exceeded and corrective actions made by each control module. The functioning of a control module, access, and storage location codes are defined in its Product Definition Description (PDD) manual.

Several case studies are presented to demonstrate the effects of control module algorithms, events, faults and actions. A complete case study identified a defect and proved that defect was the proximate cause of the injury and death. Surprisingly, these modules can seize control of a drive-by-wire vehicle and actually cause loss of control, resulting in a crash and injury ranging in severity from minor to fatal.