Buying a used car is almost always a roll of the dice. "You are just buying someone else's problems," people used to say.

The truth is that there are plenty of good used cars out there. Most cars reach the used-car market because of expiring leases or simply because owners are getting rid of their old rides for something newer, but there are exceptions. Some used cars are unloaded by their owners because of a problematic past.

When considering a used car, we always recommend getting it inspected by a qualified mechanic and obtaining a vehicle-history report from one of the several agencies offering them, such as Carfax.com or AutoCheck.com.

Unreported Damage

Even taking these precautions is not guaranteed to uncover a vehicle's every accident, however. Without taking a car apart, even an accomplished mechanic can miss signs of accident repairs. Moreover, vehicle histories only contain reported accident information. One expert told us that if an owner crashes his car into a tree, manages to get his car to a repair facility without alerting law enforcement and doesn't file an insurance claim to fix the damage, the accident probably won't show up in a vehicle-history report.

So, is there a foolproof method for identifying cars that have been in unreported accidents and for evaluating the extent of any resulting damage?

The answer is yes, and it's currently being used by accident investigators and law enforcement to aid in reconstructing accidents.

Not Exactly a Black Box

Since 2010, most new cars are equipped with an event data recorder (EDR). Although it has very little in common with the black box we hear so much about after every plane crash, that's the term most people understand when talking about the EDR.

An airplane's black box continuously records data -- often including sound -- while the plane is in operation, but the EDR is more of a snapshot of a car's data from a few seconds before an accident to a few seconds after.

During the course of an accident investigation, investigators use the crash data retrieval (CDR) tool to download EDR data to determine what the car was doing in the seconds leading up to the crash. Was it speeding, swerving or braking? Was there an airbag deployment? Were the occupants wearing seat belts?

CDR is also able to access other components that store data, such as the powertrain module, rollover sensor and airbag control module (ACM). The ACM is a virtual storehouse of crash data gathered through crash-sensing systems such as seat-belt-related sensors and occupant-detection systems.

So, What Does It Mean?

How might all of this translate into helping the typical shopper avoid damaged vehicles when buying a used car? When purchasing a used car for resale, the used-car dealer can make a CDR report part of the evaluation process. By plugging the CDR tool into the vehicle's universal data port, the user can have a printed report in hand in three or four minutes.

This can happen at the dealer's lot before accepting a used car as a trade-in, or at auctions, where dealers acquire 80 percent of the used cars that they sell. Once they've won the bid on a vehicle at an auction, dealers are provided an opportunity to inspect it before any money changes hands. If the CDR report uncovers a serious event, the dealer can opt out of the deal.

So far, used-car dealers haven't embraced CDR as a sales tool, but the day may come when used-car shoppers demand a CDR report just as they do service-history records and vehicle-history reports.

author photo

Russ Heaps began covering the automotive industry in 1986, first overseeing the automotive pages of the Boca Raton News and then the Palm Beach Post in Florida. In 2001 he became managing editor of AMI Auto Week and NOPI Street Performance Compact magazines. Since leaving AMI he has freelanced his auto reviews and industry analysis to the Washington Times, Hispanic magazine, Journal-Register Newspapers, Bankrate.com, MyCarData.com, Interest.com, and others. He resides in Greenville, SC.

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