What is a DTC? A fleet manager's guide to Diagnostic Trouble Codes

Key Takeaways

A Diagnostic Trouble Code (DTC) is a standardized alphanumeric fault code generated by a vehicle’s onboard diagnostic system when the Electronic Control Unit (ECU) detects a malfunction. Canadian fleets typically work with two standards: OBD-II for light-duty vehicles and J1939 for heavy-duty trucks and equipment. Telematics solutions read DTC data in real time and deliver alerts for the DTCs that matter most directly to fleet managers, enabling operators to act before a minor code becomes a major breakdown.