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Home >> Acura >> 1990 >> Legend LS, 2D Coupe, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Code 0, No Codes >> No Check Engine Light
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No Check Engine Light

  1. Turn ignition on. If oil pressure light is on, go to step 2). If light is off, inspect fuse No 5. Replace fuse and repair short as necessary. If fuse No. 5 is okay, repair open circuit in Yellow wire between fuse and combination meter.
  2. Turn ignition off. Connect ECU test harness between ECU and ECU connector. See Figure . Connect terminal B6 to ground. Turn ignition on. If CHECK ENGINE light is now on, go to step 3). If light is off, replace light bulb or repair open in Blue wire between ECU and combination meter.
  3. Individually, measure voltage between ECU terminals A2, A4, A16, A18 and ground. If more than one volt is present on all terminals, check open in wire between ECU and any of the terminals that read more than one volt. If less than one volt is present on all terminals, substitute a known good ECU. If problem is rectified, replace original ECU.
    NOTE: For wiring diagrams, see WIRING DIAGRAMS article. For vacuum diagrams, see VACUUM DIAGRAMS article.
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