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Entering/Exiting Diagnostic Mode

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  1. Turn ignition switch on but do not start engine. "CHECK ENGINE" light should glow. Locate assembly line data link (ALDL) connector attached to ECM wiring harness under instrument panel. Insert spade lug terminal across "TEST" terminal and "GROUND" terminal. See Fig 1 .
    CAUTION: Inserting spade lug in terminals of ALDL connector grounds "TEST" terminal lead. Do not ground ALDL connector until after ignition is on or engine is started.
    Fig 1: ALDL Connector Terminal Locations
    G9277
  2. "CHECK ENGINE" light should flash code "12". Code "12" consists of "FLASH", pause, "FLASH", "FLASH" followed by a longer pause. Trouble Code "12" will be repeated 2 more times, then if any trouble codes are stored in the ECM memory, they will be displayed in the same manner.
  3. Trouble codes will be displayed from lowest to highest numbered codes (3 times each) and be repeated as long as the "TEST"terminal of the ALDL connector is grounded.
  4. To exit diagnostic mode, turn ignition switch off and remove spade lug terminal from ALDL connector.
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