How to read diagnostic codes 101?

I see many of you discussing diagnostic codes and I'm wondering if there's a "tutorial" about these codes.

I'm wondering, for example, what equipment one needs to read these codes, how accurate are the codes when discussing a sick vehicle, do many of you check these codes on a regular basis just for good measure (or do you do it just when you have a sick truck?), etc., etc., etc.

I have a 2004 2WD Xtracab Tacoma.

Ed

 

Sub'd, would like to know also

 

Do a search for 'code reader' (titles only)

 

A scanguage also will tell you codes. You get the code and then you can better figure out or pinpoint the problem. https://www.scangauge.com/products/scangaugeii/