In an industry with very few standards, ASE is the most universally recognised testing/certifying body. Originally organised in around 1973 (I know because I was a dealer Chevrolet technician at the time I got my Master's in 1973) as the NIASE: National Institute for Automotive Sevice Excellence.
Originally testing was in only eight areas. They now test body men, parts countermen (maybe I should say persons) and heavy truck. About 4-5 years ago they added the ultimate for driveability techs the L1. A master is one who has certified in all 8 automotive areas. In original testing for L1 only 25% of Masters passed the test.
To be ASE certified one must pass the test and pass an experience standard. I think the experience standard is two years as a professional technician. While there are many training programs to pass the tests, they are mainly designed to teach test taking and interpreting various styles of questions. These courses would not be taken to learn auto technology specifically.
For more information see: http://www.asecert.org/