About Freeze Frame
Short answer: Every code page follows the same structure: what the computer actually measured, the likely causes ranked by frequency, the one measurement that separates cheap repairs from expensive ones, and the tests ordered cheapest and most likely first.
The ordering principle
Diagnostic steps are ordered by cost and probability, not by the order a parts catalogue lists components. The expensive part is almost never the first thing to check, and the most common failure is rarely the most expensive one. Following the order on these pages is designed to stop you buying a catalytic converter when the fault was a thirty dollar sensor or a torn hose.
Why every page has a graph
Most codes come down to a single measurement that splits the possible causes into groups. On P0420 it is whether the downstream oxygen sensor mirrors the upstream one. On P0171 it is whether fuel trim rises or falls with engine speed. Those graphs are the fastest route to the right half of the problem, so they get their own section.
What these guides are not
They are general reference for standardised generic codes. They are not a substitute for the factory service manual for your specific year, make, model and engine, and they do not carry vehicle-specific torque values, wiring diagrams or procedures. Confirm anything you intend to actually do against the manual for your vehicle.
Corrections
If something here is wrong, or your vehicle behaves differently in a way worth documenting, that is genuinely useful. The comment section on the matching video is the fastest place to raise it.