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Home >> Oldsmobile >> 1979 >> Omega Base, 2D Hatchback, 3.8L Eng VIN A, Automatic Trans >> Repair and Diagnosis >> Engine Performance >> Engine Control Systems >> Computer Controlled Catalytic Converter >> Testing & Diagnosis >> "Check Engine" Light Test
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"Check Engine" Light Test

  1. Ensure the C-4 diagnostic system is operating properly, turn off ignition switch, leave engine stopped, and ground the trouble code (White/Black) test lead.
  2. If system is operating properly, the "CHECK ENGINE" light will flash Code 12, which indicates proper operation. See Figure chart.
    NOTE: If fault is intermittent, "CHECK ENGINE" light may come on and then go out; however, fault problem will be stored in ECM memory so diagnosis can be performed.
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