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Home >> Geo >> 1990 >> Prizm Base, 4D Hatchback, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Diagnostic Circuit Check >> Chart A-1, No Check Engine Light >> Notes

Chart A-1, No Check Engine Light: Notes

With ignition switch in the ON position and engine off, CHECK ENGINE light should always be on. The ECM controls the CHECK ENGINE light by completing bulb ground circuit.

NOTE: Test numbers refer to test numbers on diagnostic chart.
  1. An open GAUGE fuse could indicate a short to ground in GAUGE fuse circuit.
  2. This indicates a ground path through the ECM.