Definition: The name given to fault codes or trouble codes that are read by counting flashes of the Check Engine light or ABS warning light. Though not available on some systems, flash codes provide essential diagnostic information for troubleshooting problems. To read any codes that may be stored in the control module's memory, the computer system must first be put into a special diagnostic mode by grounding a terminal on the vehicle's diagnostic connector. The codes are then flashed out via the light. By carefully counting the flashes and pauses, a numeric code is deciphered that tells you which diagnostic chart to refer to in the service manual. A series of step-by-step checks must then be made to isolate the faulty component.

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