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Code 18: Ignition Timing Adjuster

  1. Turn ignition off. Remove BACK-UP fuse (10-amp) from underhood fuse/relay 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 the control box. See Fig 1 . Measure resistance between terminals "A" and "C" of ignition timing adjuster.
    Fig 1: Identifying Ignition Timing Adjuster Connector Terminals
    G92H26218Courtesy of AMERICAN HONDA MOTOR CO., INC.
  3. If resistance is 3500-6500 ohms, 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. If total resistance is not 3500-6500 ohms, replace ignition timing adjuster.
  5. If resistance is 3500-6500 ohms, turn ignition on. Measure voltage between Yellow/White (+) and Green/White (-) wire terminals on harness side of connector. If voltage is not about 5 volts, proceed to step 8).
  6. If voltage is about 5 volts, measure voltage between body 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 5 volts, turn ignition off. Connect ECM Test Harness (07LAJ-PT3010A ) between the ECM and ECM connectors. See Figure . Turn ignition on. Measure voltage between ECM terminals D20 (+) and D22 (-). If voltage is about 5 volts, repair open in Yellow/White wire between ECM connector terminal D20 and ignition timing adjuster. If voltage is not about 5 volts, replace ECM and retest.
  8. If voltage in step 5) was not about 5 volts, turn ignition off. Reconnect ignition timing adjuster 3-pin 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 Brown 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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