Ever trace a short circuit without the correct wiring diagram? Or tightened cylinder head bolts not knowing the torque specifications? Probably not. That's why having the manufacturer's auto repair information in hand's reach is so important. Whether you're an experienced automotive technician, or an owner who likes to do car maintenance and repairs on your own, the correct service and repair information can be the most important addition to your toolbox.
Auto repair manuals include a wide variety of information such as wiring schematics, torque specifications, diagnostic trouble codes, repair & replace procedures, step-by-step diagnostic guides, and a lot more.
Companies compile car and truck repair manual information from the manufacturers and make it available online in various formats, most including Recalls & Technical Service Bulletins. These systems are comprised of a good part of the manufacturer published materials. Distributers like ALLDATAdiy.com supply a large number of independent repair shops across the country with gotta-have service information, and also provide online model-specific packages for do-it-yourselfers, at reasonable prices.
Nobody knows a car, truck or SUV better than the manufacturer (engineers) who built it. So we want to use materials originally published by the maker of the vehicle we're working on, like the online DIY programs.