TNM Engineering, LLC
725 S. Mesa Hills, Bldg 2 Suite 4
El Paso, TX 79912
Office: 915-533-4041
Fax: 915-533-6653

ECM Download Authorization Form
Commercial Vehicle ECM Download, Data Extraction & Interpretation
While downloading “black box” data from passenger vehicles is becoming more common in the accident reconstruction community it is important to know that “black box” data also exists in commercial vehicles. The commercial vehicle “black box” is known as the Electronic Control Module or ECM and is the computer that controls the engine functions. The data that can be obtained by downloading a commercial vehicle is not dependent on the manufacturer of the vehicle but the manufacturer of the engine. Engines manufactured by Detroit Diesel, Caterpillar, Cummins, Volvo and Mack all contain varying amounts of information that can be useful in the reconstruction of commercial vehicle accidents.

Most current ECM’s have the capability to record and report data when a pre-programmed rate of deceleration occurs. The data that can be extracted from certain ECM’s include vehicle speed, engine RPM, % throttle application, brake application, clutch application, cruise control activation, % engine load and more. This data, in some ECM’s, is reported for up to two minutes prior to an event and fifteen seconds after. The engine speed governor setting can also be extracted from the ECM and used to place an upper limit on the vehicles road speed during a crash.
Detroit Diesel ECM’s can provide crash data in the form of a “Last Stop” report and a “Hard Brake” report on certain ECM models. The “Last Stop” report is generated when the vehicle comes to a complete stop and provides one minute and forty five seconds of pre-stop data and fifteen seconds of post-stop data. This report will be overwritten once the vehicle is driven. To obtain this report it must be downloaded before the vehicle is driven from its final rest position. The vehicle can be downloaded away from the crash scene provided the vehicle is towed with the drive shaft disconnected to avoid the possibility of the ECM recording a vehicle speed. The “Hard Brake” report is recorded when the vehicle slows at a pre-programmed deceleration rate which is set from the factory at seven miles per hour per second. This report provides one minute of pre-event data and fifteen seconds of post-event data. The Detroit Diesel ECM stores the two most recent “Hard Brake” reports. A date and time notation is recorded with each “Hard Brake” and “Last Stop” report. Additional information may also be extracted from the ECM depending on conditions.
Cummins ECM’s provide crash data in the form of a “Sudden Deceleration” report on certain newer ECM models. The Cummins ECM does not provide a “Last Stop” report like the Detroit Diesel however is does is does store the three most recent “Sudden Deceleration” events. The “Sudden Deceleration” report provides one minute of pre-event data and fifteen seconds of post-event data. The Cummins ECM does not provide a date and time stamp with each event however it does include an odometer reading. It is best to download the ECM either at the scene or after it has been towed from the scene.
Caterpillar ECM’s are capable of recording crash data in the form of a “Quick Stop” or a “Snap Shot” report. Unfortunately, the Caterpillar ECM leaves the factory with the “Quick Stop” recording feature turned off. This feature must be turned “on” BEFORE the incident in question for the recording feature to operate. The Caterpillar ECM can record a “Snap Shot” of a critical event such as a loss of oil pressure. It is possible in some instances to capture a “Snap Shot” of a crash if the engine loses oil pressure with the engine running. Such an event could occur if the oil pan is damaged by running over an object near the time of the crash. Other critical events can also cause the generation of a “Snap Shot” report.

It is important to have a forensic download of the ECM to ensure that the data is downloaded completely. It is common for service facility downloads to be incomplete since some ECM’s require the use of more than one software program to extract all the data contained in the ECM. TNM Engineering is equipped to conduct “In-Cab”, “On Engine” and “Off Engine” downloads of Detroit Diesel, Caterpillar and Cummins ECMs.

The ECM download data can be invaluable to the understanding of a crash since it provides data that could not be obtained through typical reconstruction methods. However, it is only a tool that should be used in conjunction with a vehicle inspection and crash reconstruction.

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