Allegations of automobile malfunctions having caused an accident are often the basis for a claim against an automotive repair facility. The scenario usually develops as follows. An automotive repair facility works on a vehicle and releases it to the owner after the repair has been completed. Shortly afterward, the vehicle is involved in an accident and the driver blames the accident on an automobile malfunction related to the recent repair. One repository of factual information that will help evaluate such a claim resides in the onboard memory of the sensing diagnostic module (SDM) of the vehicle, often called the black box.

Figure 1 is a view of a vehicle that struck another vehicle in the rear end. The driver claimed that the engine stalled, causing reduction in power brake assist and an accident. The repair shop had performed ignition work on the engine a few days prior to the accident.

Figure 2 shows the data dump from the sensing diagnostic module of the vehicle. The green line on the graph is engine RPM, which was approximately 1300 RPM up to 3 seconds before algorithm enable (AE) or air bag deployment. The driver then pressed the brake pedal at 3 seconds before AE and severe braking was achieved, as indicated by the deceleration of the vehicle in the red line on the graph. The driver had taken a foot off the accelerator and pressed the brake at 3 seconds before AE. Engine RPM decreased to 800 RPM, which is typical idle speed, suggesting that the engine did not stall. Clearly the SDM data is contrary to the claim that the engine stalled and consistent with the proper operation of the engine. The claim against the repair shop was denied.