According to a recent J.D. Power and Associates study, sales of certified used cars have increased 46 percent since 2000. For many people, certified used cars have become affordable alternatives to new cars. By "certified used" or "certified pre-owned," we mean used cars that are offered for sale by your local dealer and feature warranties that extend beyond the initial "when new" coverage.
To qualify for our definition of a "certified used" vehicle, the warranty must be backed by the original vehicle manufacturer. The original manufacturer of the vehicle is using its dealer network to inspect the car, determine if it is worth certifying and then offer support for the vehicle for a period of time beyond the original warranty. Not all used cars can qualify for certified pre-owned programs, and terms vary from one brand to the next, but any true certified pre-owned program will include at least a 100-point inspection of the car. If problems are found, the factory-trained technicians will fix it or disqualify the car from the program. The certified warranty protection typically takes effect when the original warranty expires and, like a new car warranty, offers coverage for a certain number of years or miles, whichever comes first.
See
http://www.edmunds.com/advice/cpo/ar...9/article.html
Be careful of those claiming "certified" that offer third party warranties.