Glossary
Diagnostic Trouble Code (DTC)
A standardized alphanumeric code (e.g. P0299) that a vehicle's computer sets when it detects a fault, pointing a technician toward the affected system and circuit.
A DTC's first letter identifies the system (P for powertrain, B for body, C for chassis, U for network), and the digits narrow it to a specific circuit or condition. A code says what was detected, not necessarily what part caused it — that's where diagnosis starts, not ends.
See also
- OBD-II: The standardized on-board diagnostics system, mandatory on US-market vehicles since 1996, that reports diagnostic trouble codes and live sensor data through a common 16-pin connector.
- Malfunction Indicator Lamp (MIL): The dashboard warning light — usually shaped like an engine outline — that illuminates when the onboard computer detects and stores a diagnostic trouble code.
Guides that use this term
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