Everyone has heard of the “black box”, it’s always the topic of conversation and the world’s scrutiny whenever a commercial or military plane goes down. It holds all of the secrets of the last fateful trip and is always equipped with some sort of transponder or homing device to make it easier to find. It can monitor conversations from the pilots to each other and to any towers; it monitors all of the vital information for the flight, such as speed, altitude, all mechanical and electrical communications within the plane itself so investigators can determine the cause of the plane’s malfunction. Like it or not, the safest way to travel rarely has any survivors when one goes down.
Recently I read a story about a motor vehicle accident, I must be honest with you, I read it quickly and picked up the general theme, but I did not examine it closely. This story was dealing with an accident that had no witnesses, one person dead, and the driver. I’m not really sure if it was a hit and run or not but prosecutors have retrieved the vehicle “black box” and with it gained not only a “witness” to the accident but a wealth of information regarding the operation of the vehicle right before the incident, as with Tiger Woods.
This “black box” that has become the star witness, in this case, is what we refer to in the automotive industry as an abuse counter. Usually installed in high-end vehicles or vehicles that are built to become rentals, it recalls and saves key pieces of information that the owners of these vehicles have deemed important to the resale and upkeep of these vehicles. The most commonly recorded items are average speed, the number of wide-open throttle requests, the number of anti-lock brake stops, and impact sensor reactions. Thus, the name “Abuse Counters”.
However what you probably never realized is that if you own a vehicle that was built or sold in the United States after January 01, 1996, it has a flight recorder in it. This type of recorder is a little different than most. This is what we refer to as a Freeze Frame. Back in the nineties, it was very basic, usually recording power train issues. Today every control module that is in your vehicle is constantly monitoring data for whatever system it is in charge of. Transmission and engine modules most typically referred to as power train control modules, or PCM’s monitor all of the sensors and circuits involved in the operation of these components. I decided to concentrate on these modules first because it these modules that usually turn on the check engine lamp.
As soon as the module finds and triggers a code, the freeze-frame captures that moment. It gives us a huge amount of data such as ambient temperature, rpm’s, vehicle speed, fuel trim, and load conditions. This helps us as technicians to gain extra information so that we are able to diagnose the problem more accurately, especially when it is an intermittent problem. One such vehicle that proved invaluable to us was a Toyota that was forever registering a lean condition code but was never running lean when it finally came to us. After researching this issue we found that this particular engine had an issue with the intake manifold gaskets and when the ambient temperature dropped below a certain point the intake manifold would contract enough to cause a vacuum leak, and as the vehicle warmed up, the manifold expanded enough to shut the leak-off. So what we eventually did was clear out all of the codes, reset all of the monitors, and waited for the light to come back on. Because we knew that the code would be recorded the owner was able to come back to the shop at her convenience where we examined the saved data to confirm the diagnosis and repaired it right the first time.
The second most important time this information is used is in the event of a collision. This is most crucial when it is a single-vehicle collision and when the driver has been terminally injured or impaired by any other reason other than alcohol. Whenever an airbag is activated there is a huge amount of information shared by multiple modules to prevent accidental deployment. When an airbag module requests permission to activate an airbag, the PCM first looks at the ABS module, the transmission module, and the body control module, making sure that the wheels are slowing down, and in some cases, the ABS has recorded an event. It looks to the transmission for a rapid downshifting that should occur if a vehicle is slowing down and the body control module to make sure that the brake lights are on. It then monitors its own engine sensors to check if the throttle body is closed, and if the intake manifold vacuum has maxed out, as well as a sharp decrease in outside air volume that is going past the mass airflow sensor. Having checked all of this information and deciding that yes the vehicle is involved in a collision allows the airbag sensor to deploy the airbag. Amazingly enough, this whole process takes all of 500 milliseconds.
This is important because as a technician and sometimes as an investigator, it allows me to look forensically to substantiate the cause of an accident and try to determine if it was caused by driver error or mechanical failure, which can mean the difference of a long prison term or not. Sometimes mechanical failures are caused by economic issues, or just ignorance, and every so often by blatant disregard for the safety of themselves or others on the road.
Preventive maintenance and scheduled safety inspections are not an upsell, sometimes it is the difference between someone’s life or death.