LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Acura >> 1990 >> Legend Base, 4D Sedan, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Code 0, No Codes >> Check Engine Light On, Red Led Does Not Flash
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Check Engine Light On, Red Led Does Not Flash

  1. Turn ignition on. One at a time, remove for at least 10 seconds and inspect alternator sense, ECU and fuel pump fuses. Replace and repair short as necessary. If fuses are okay, try to start engine. If engine won't start, leave ignition on. If engine starts, shut off and turn ignition on.
  2. Check to see if CHECK ENGINE light is on after 2 seconds. If light is not on, failure is intermittent. System is okay at this time. Check for poor connections at ECU fuse, fuel pump fuse, main relay and ground 102. If light is on, check to see if ECU Red LED is indicating any trouble codes.
  3. If codes are present, see TROUBLE CODES  diagnostic procedure. If codes are not present and engine started in step 1), turn ignition switch off. Disconnect connector "B" of ECU. Turn ignition on. If CHECK ENGINE light is on, repair short to ground in Blue wire between terminal B6 and combination meter.
  4. If CHECK ENGINE light is not on, substitute a known good ECU and recheck. If system works properly, replace original ECU. If engine did not start, turn ignition on. Disconnect the 3-pin connectors one at time on MAP, throttle angle and EGR position sensors.
  5. If CHECK ENGINE light goes out, replace sensor that caused CHECK ENGINE light to go out. If CHECK ENGINE light stays on, reconnect all connectors. Disconnect ignition timing adjuster connector. Check to see if ECU Red LED indicates Code 18. If Code 18 is indicated, replace ignition timing adjuster.
  6. If code 18 is not indicated, reconnect ignition timing adjuster connector. Turn ignition off. Connect ECU test harness but disconnect ECU connector "C". See Figure . Check for continuity individually between terminals C13, C15 and ground.
  7. If continuity exists, repair short to ground in Yellow/White wire between terminal C13 and PA sensor, ignition timing adjuster, throttle angle sensor or EGR lift sensor. Repair short to ground in Yellow/White wire between terminal C15 and MAP sensor.
  8. If continuity does not exist, reconnect connector "C". Disconnect connector "B" from ECU side only. Turn ignition on. Individually, measure voltage between ECU terminals A16 and A18 to ground. If reading is one volt or more, repair open in Brown/Black wire between terminal A18 and ground 102.
  9. Repair open in Brown/White wire between terminal A16 and ground 102. If reading is less than one volt, measure voltage between ECU terminals A15 and A18. If battery voltage is not present, repair open in Yellow/Black wire between ECU terminal A15 and main relay, or check main relay and wire connectors at main relay.
  10. If battery voltage is present, turn ignition off. Substitute a known good ECU. Turn ignition on. check to see if CHECK ENGINE light remains on after 2 seconds. If light is on, replace PA sensor. If light shuts off, replace original ECU.
scientia non olet · About LEMON Manuals