Engine Control Modules, Air Bag Control Modules
& Event Data Recorders

Electronic controls were introduced into small trucks and automobiles to monitor the vehicle accelerations and analyze the data to determine when an accident is occurring and whether it is serious enough to deploy the airbags. The time frame to accomplish this is very short, on the order of 25 milliseconds. These modules may continue to monitor the accelerations after the deployment of the airbag.

Typical Stopping Decelerations for Hard Braking/Skidding

G’s MPH/S

Dry Level Pavement 0.70 – 0.80 15 - 18 Automobile/Small Truck
0.45 – 0.60 10 - 13 Large Truck

Wet Pavement 0.40 – 0.60 8 - 13 Automobile/Small Truck
0.40 – 0.50 8 - 11 Large Truck

Soil / Dry Grass 0.40 – 0.50 8 - 11 All Vehicles

Rolling or Overturned 0.40 – 0.50 8 - 11 All Vehicles
Ice / Snow 0.05 – 0.20 1 - 5 All Vehicles

Typical Low Speed Accelerations

G’s MPH/S

Automobile/Small Truck         0.10 – 0.40      2 - 9
Large Truck                           0.05 – 0.15     1 - 3

Airbag Control Modules (ACM)

Typically record:
   Seat belt status
   Longitudinal collision accelerations/delta v
   Airbag faults if present

May record:
   Speed, RPM, throttle, braking before collision
   Longitudinal collision accelerations/delta v
   Multiple events
May capture data from event even if the airbags did not deploy
Other parameters

ACM, PCM, ROS

General Motors Fiat/Lancia Ford Izuzu Chrysler Saab Toyota Scion Mitsubishi Suzuki Sterling

Download Hardware/Software - Currently Not Commercially Available
Audi Nissan BMW Porsche Honda Volkwagen Mazda Volvo Mercedes

Engine Control Modules (ECM)

Cummings Detroit Diesel Caterpillar Mack International Volvo Paccar Mercedes

Electronics were introduced into the heavy truck engines to control emissions, the engine, the powertrain, and monitor the status of the primary engine operations primarily for maintenance purposes. Some of the functions such as speed, rpm, throttle and brake status are directly applicable to the analysis and reconstruction of an accident.

Heavy truck engine manufacturers use different terminology for their particular module(s). MCM, VECU, ECU etc. all refer to the same basic components. Some manufacturers use a single module bolted to the engine. Others use two or three separate units. These can be located on the engine, frame or in the cab. Multiple units are typically split with one on the engine and the others in the cab.

Software/hardware
Every manufacturer uses their own proprietary software.
   In cab connections are standardized ( 6pin or 9 pin) but may require separate hardware to access
   Direct to ECM connections require separate cables and other hardware
   Will provide large amounts of data on the engine and its operation.
   May provide information on speed, RPM, braking, throttle, etc. before, during and after the collision.
   Speed data comes from the VSS (vehicle speed sensor) that monitors the drive shaft rotation.

Decisions to be Made with respect to altering the ECM Data after and Accident
   Should the vehicle be moved under its own power?
   Should the vehicle be moved under its own power?
   Should a download be attempted on a damaged vehicle?   If so how?
   Does downloading alter the data?
   Can the module be removed to preserve the data?

Powertrain Control Modules (PCM)

Automobiles and small trucks typically have an electronic module that controls the powertrain. These are similar in size and function to the heavy truck ECM.

Rollover Sensors (ROS)

Electronic controls were introduced into vehicles to monitor lateral accelerations for both side airbag deployment and stability control. Some of this data may be captured and available for download. Stability control is becoming increasingly prevalent in small vehicles and is beginning to appear in heavy trucks.

ROS in automobiles is accessed with the CDR system. In heavy trucks, ROS is typically associated with the stability control and part of the braking system.

Event Data Recorders (CDR)

Other types of devices may provide information:
   Vorad collision avoidance and warning
   Wingman
   GPS tracking
   ABS brake systems
   PeopleNet
   QualComm
   EasyPass
   Electronic Logbook
   VORAD
   Vehicle Onboard Radar

Vorad Collision Avoidance and Warning

It was Developed and implemented by Eaton, and is now owned by Bendix. It was iIntroduced in 1992. Download information has been available since 1995. It provides early warning to drivers (lights/sounds) of vehicles evaluated as hazards either by proximity or closure rate. Downloads are a commercial service provided by the manufacturer.

Downloads ECM and ACM Equipment

Engine Control Modules, Air Bag Control Modules& Event Data Recorders