For years, professional auto technicians have relied on the good old automotive repair manuals. These books cost hundreds of dollars for a set for just one model of car or truck.
Considering that during any given year, GM car lines may have 5-20 different models. Lets say that in 2001 Chevrolet had 20 different models, and Buick had 5. Keeping a library up to date got to be very expensive. Consider that every single year, things change on the same car. Sometimes these changes took place in the middle of the production year.
Things were even tougher for the do-it-yourselfer, or "Backyard Mechanic". They had to purchase automotive repair manuals published by 3rd party companies. Many times the info was vague, misleading, or just plain wrong.
Things changed several years ago on how GM dealer Technicians get the manuals needed to repair todays very complicated cars and trucks. The auto makers went to a computer CD based service manual. This was much better for the younger guys, since they are very accustomed to using personal computers. Not so much to some of the older Tech's. Every few weeks we would get an update CD to add changes to the vehicles as was needed. This is also how we received our Technical Service Bulletins (TSB) and Recalls. This was not much help to the average guy working on his own vehicle.
Today, all manuals for Dealers are completely web based. All schematics, service bulletins, recalls, manual updates, etc. are delivered right to our in house computer system automatically. These updates happen every single day. A huge improvement from years past. There has been times where I am working on a customers car and cannot duplicate the intermittent condition. I had the car for a day or two, only to have no choice but to give him his vehicle back. 3 days later in acts up again with the same problem. Now this time our system has been undated several times and there is all of a sudden a TSB for this illusive problem. Now, it takes me just a few minutes to fix the problem, even though it is not acting up for me, because I know this bulletin will address the problem.
This technology has also found its way to the average auto shop and home mechanic in his own garage. Similar systems can be purchased on a monthly basic, or a year subscription. Examples of these are Haynes, ALLDATA, Chilton, Mitchell, Motors, just to name a few. There are also tons and tons of free information out there on the web. Much of it is not actual repair manual pages, but mechanics sharing their knowledge- these are called Forums. Sometimes these are helpful, other times not, as anyone can sign up as an "Expert Mechanic, even though no checking done to see if this is the case. Most of these forums are people exchanging their past auto repair experience.