� Related Terms ��OBD-II � �

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. 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.