When a vehicle must be diagnosed, the technician will establish a diagnostic strategy based on the observed symptoms. There are a few general starting points which are assigned according to what the vehicle will, or will not do. For instance, a vehicle that will start, but the engine immediately stalls is called a "start and stall" issue, and a specific diagnostic process is used to identify the cause of the condition. It is important to keep in mind that general diagnostics will lead to another form of diagnostics once the issue is able to be categorized according to the system that is causing the failure.

Corrections for general diagnostics issues usually involves replacing simple components, such as the battery, alternator, a blown fuse, or a bad coil. However, due to the wide variety of components that can possibly cause a problematic condition, repairing this issue could involve replacing a fuse, or replacing the engine, and repair procedures are on a case-by-case basis.

Diagnostics in general can be problematic, and there are many variables to account for when the issue, or the cause of this issue is unknown. When problems arise, diagnostics may take several hours to complete, or just a few minutes. This will significantly impact the cost of repairs. Choosing a facility with proper equipment and training for their staff may significantly reduce diagnostic time needed.

Diagnosing modern automotive systems without proper knowledge and training can be frustratingly difficult, but without proper technique the diagnosis will only be reached through changing parts on a hunch. Automotive systems, especially in the last several years, have become extremely advanced, and most vehicles have a communication network that allows all of the systems to communicate. This is a blessing for the trained technician, and a curse for the DIYer who would rather save money on the repair.

General diagnosis should be attempted by the experienced DIYer, with a good understanding of all affected vehicle systems, and the proper tools and techniques to diagnose a variety of issues. The task of diagnostics should be left to a professional technician once all knowledge and tooling resources are dissolved, as damage may occur without excellent knowledge, skill, and tooling.