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Home >> Acura >> 1991 >> Legend Base, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Code 0, No Codes >> Check Engine Light Stays On
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Check Engine Light Stays On

  1. Turn ignition on. Connect jumper wire to diagnostic connector. Check to see if ECU flashes any trouble codes. If any codes are present, see appropriate TROUBLE CODES diagnostic procedures. If codes are not present, remove jumper wire.
  2. Try to start engine. If engine won't start, go to step 6). If engine starts, turn ignition off. Connect ECU test harness between ECU and harness. Turn ignition on. Measure voltage between terminals C9 and A26 of ECU connector. If about 5 volts are present, go to next step. If about 5 volts are not present, repair short to body ground in White wire between terminal C9 at ECU and diagnostic connector.
  3. If about 5 volts are present, connect jumper wire to diagnostic connector. If about 5 volts are now present, check for open in White and Black wires between diagnostic connector and ECU. Repair any problems.
  4. If about 5 volts are still not present, remove jumper wire from diagnostic connector. Turn ignition off. Disconnect connector "A" of ECU. Turn ignition on. If CHECK ENGINE light is on, repair short to ground in Blue wire between terminal A13 and combination meter.
  5. If CHECK ENGINE light is not on, substitute a known good ECU, and recheck. If system works properly, replace original ECU.
  6. If engine does not start, check fuses No. 5 and IG COIL in underdash fuse box. Replace any bad fuse(s). Turn ignition on. Install jumper wire to diagnostic connector. Individually disconnect 3-pin connectors on ignition timing adjuster and MAP, throttle angle and EGR position sensors.
  7. If CHECK ENGINE light goes out, replace sensor causing CHECK ENGINE light to go out. If CHECK ENGINE light flashes, reconnect all connectors. Disconnect throttle angle sensor or ignition timing adjuster connector. Check to see if ECU flashes Code 7 or 18. If Code 7 is indicated, replace throttle angle sensor. If Code 18 is indicated, replace ignition timing adjuster.
  8. If Code 7 or 18 is not indicated, turn ignition off. Remove diagnostic jumper wire. Connect ECU test harness between ECU and harness. Disconnect connector "D" from ECU side only. See Figure . Individually check for continuity between ground and terminals D19 and D20.
  9. If continuity exists, repair short to ground in Yellow/White wire between terminals D19 and D20 and MAP sensor, ignition timing adjuster, throttle angle sensor or EGR lift sensor.
  10. If continuity does not exist, reconnect connector "D". Reconnect all sensor connectors. Turn ignition on. Individually measure voltage between ECU terminals A25 and C1 to A26 (negative). If battery voltage is not present, repair open in Yellow/Black wire between main relay and ECU terminals A25 and C1.
  11. If battery voltage is present, turn ignition off. Substitute a known good ECU. If problem goes away, replace ECU.
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