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Diagnostic Trouble Code (DTC) FinderThis page contains links to articles on www.AA1Car.com that deal with diagnostic trouble codes (DTC), fault codes, and onboard diagnostics using scan tools and scanner software.
Computerized engine control systems have the self-diagnostic capability to detect faults that may affect engine performance and emissions. When a fault is detected, the computer will store a diagnostic trouble code in its memory and illuminate the Check Engine Light or Malfunction Indicator Lamp (MIL). On older vehicles (mostly pre-1996), the computer can be put into a special diagnostic mode by grounding certain terminals on a diagnostic connector. This will trigger the manual flash codes to display. The Check Engine Light or other lights will then flash out the fault code. On newer vehicles (1996 and up with OBD II), a code reader or scan tool must be plugged into the diagnostic connector to read and erase codes.
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