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DIAGNOSTIC TROUBLE CODE
Definition: Computerized engine control systems have a certain amount of built-in self-diagnostic capability to detect problems that affect engine performance and emissions. The same is true for the antilock brake system and other onboard systems that are computer controlled.
Related Terms
OBD-II

When a fault is detected, the computer will store a diagnostic trouble code in its memory and illuminate the "Check Engine" light. On some vehicles, the computer can be put into a special diagnostic mode by grounding certain terminals on a diagnostic connector. This will cause the Check Engine or other lights to flash out the fault code. On many vehicles, though, a scan tool must be plugged into the computer system to access and read the codes.

Related Resources:

Diagnostic Trouble Codes
How to display and read the Diagnostic Trouble codes stored in your vehicles computer.

OBD-II Diagnostic Trouble Codes
A listing of all generic OBD-II diagnostic trouble codes.

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