DTC fault codes are easy way of letting you know that your engine has a problem. Every sensor and circuit on your engine has a certain expected reading and voltage signal.
DTC, as you can already surmise from the title, is an acronym for "Diagnostic Trouble Codes".
Today's computerized engine control system can up to a certain point self-diagnose to detect auto problems
that could be affecting your vehicle's emissions and engine performance.
This also goes for the onboard systems and the antilock brake systems controlled by your engine's computer.