A DTC (Diagnostic Trouble Code) is the standardised code a vehicle stores when a monitored system detects a fault — the starting point of most diagnostic work.
Codes follow a structured format (like P0301 for a cylinder-specific misfire) with standardised generic codes and manufacturer-specific extensions. Reading codes is universal; the value of better tools lies in live data, guided tests and the functions needed to fix and clear what the code points to.
Why it matters
“Reads codes” is the floor, not the feature: buyers comparing tools should look at what happens after the DTC — data access, bi-directional controls and repair information.
Related terms: OBD-II, SGW · Related reading: Choosing a diagnostic platform