1993 Acura Legend Base, AutomaticFACTORY OEM SERVICE PROCEDURE

Code 18: Ignition Timing Adjuster

  1. Turn ignition off. Remove ACG fuse (No. 15, 7.5-amp) from underdash fuse box for 10 seconds to reset ECM. Check ECM for fault codes. If Code 18 is not present, problem is intermittent. Check for poor connections at ECM connector and ignition timing adjuster connector. Test drive vehicle and retest.
  2. If Code 18 is present, turn ignition off. Disconnect ignition timing adjuster 3-pin connector from control box. See Fig 1 . Measure resistance between terminals "A" and "C" of ignition timing adjuster.
    Fig 1: Locating Ignition Timing Adjuster Connector
    G91F16290Courtesy of AMERICAN HONDA MOTOR CO., INC.
  3. Resistance should be 3500-6500 ohms. If resistance is as specified, go to step 4. If resistance is not 3500-6500 ohms, replace ignition timing adjuster.
  4. Measure and record resistance between terminals "A" and "B" on timing adjuster side of harness connector. Measure and record resistance between terminals "B" and "C" on same side of connector. Add both resistance values together.
  5. If total resistance value is not 3500-6500 ohms, replace ignition timing adjuster. If resistance is 3500-6500 ohms, turn ignition on. Measure voltage between Yellow/White (+) and Green/White (-) wire terminals on wiring harness side of connector. If voltage is about 5 volts, go to step 8.
  6. If voltage is not about 5 volts, measure voltage between ground and Yellow/White wire terminal. If voltage is about 5 volts, repair open in Green/White wire between ECM terminal D22 and ignition timing adjuster connector.
  7. If voltage is not about 5 volts, turn ignition off. Connect ECM Test Harness (07LAJ-PT3010A ) between ECM and ECM connectors. See Figure . Turn ignition on. Measure voltage between test terminals D20 (+) and D22 (-). If about 5 volts are present, repair open in Yellow/White wire between ECM terminal D20 and ignition timing adjuster. If voltage is not about 5 volts, replace ECM and retest.
  8. If voltage between Yellow/White and Green/White wire terminals in step 5 was about 5 volts, turn ignition off. Reconnect ignition timing adjuster connector. Connect ECM Test Harness (07LAJ-PT3010A ) between ECM and ECM connectors. See Figure .
  9. Turn ignition on. Measure voltage between ECM terminals D8 (+) and D22 (-). If voltage is not 0.5-4.5 volts, repair open or short in Blue/Yellow wire between ECM connector terminal D8 and ignition timing adjuster. If voltage is 0.5-4.5 volts, replace ECM and retest.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.