The free diagnostic check of automatic zones is not very reliable. What they call diagnostic testing is simply hooking up a code scanner to the vehicle’s computer. The scanner reads and detects error codes recorded by the computer system.
Can AutoZone tell you what’s wrong?
If your check engine light is on and you need to figure out what’s wrong, go to your local AutoZone and ask for Fix Finder. Fix Finder reads diagnostic trouble codes from your vehicle’s on-board diagnostics system and extracts your vehicle’s information and mileage.
Is a vehicle diagnostic test worth it?
However, many technicians recommend taking your car for a diagnostic check at least once a year, which will uncover minor problems that aren’t visible or audible (and won’t trigger the check engine light). Diagnostic tests are also a useful tool when inspecting a used vehicle. 18