DTC or the Diagnostic Trouble Codes are specific codes used by manufacturers to diagnose certain problems in a vehicle. These are the codes OBD-II scan tools identify and communicate with technicians to help them pinpoint the exact areas of your vehicle's issues. The DTC can be accessed using FORScan. In a video by hackfreehvac, he showed how to diagnose a bad transmission on a Ford E Series van by checking the DTC using FORScan.

OBD or On-Board Diagnostic is a system that enables the car’s computer set-up to interface with external electronics. Its main functions are for self-diagnostic and reporting of the car’s condition and overall performance. OBD allows vehicle owners and technicians to determine specific areas that require repair or unlock certain functions to improve performance.