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Diagnostic Circuit Check (Except ECM/BCM Equipped Vehicles): CARBURETED: Notes

  1. Check SERVICE ENGINE SOON light operation. With ignition on and engine off, light should be on steady. If light illuminates and stays on steady, go to next step. If light does not illuminate, go to SERVICE ENGINE SOON LIGHT INOPERATIVE. If light flashes, go to step 3).
  2. Grounding the ALDL "test" terminal should cause SERVICE ENGINE SOON light to flash a Code 12, followed by any codes stored in ECM memory. If light goes from bright to dim, this is not considered a code. If lights dims or remains on, see SERVICE ENGINE SOON LIGHT ON OR WON'T FLASH CODE 12.
  3. If light begins to flash as soon as ignition is turned on, check for a short to ground on the diagnostic test terminal wire between ALDL terminal "B" and ECM terminal No. 5. If circuit is okay, replace ECM.
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