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Code 12: EGR System (1.8L)

  1. Turn ignition off. Remove BACK UP fuse from underhood fuse/relay box for 10 seconds to reset ECU. Warm engine until cooling fan comes on. Road test vehicle for about 10 minutes, keeping engine speed approximately 1700-2500 RPM. Check ECU for fault codes. See RETRIEVING CODES  . If Code 12 is not present, problem is intermittent. Check for poor connections at ECU connector and EGR valve connector.
  2. Test drive vehicle and retest. If Code 12 is present, start engine. Disconnect vacuum No. 16 hose from EGR valve. See Fig 1 . Connect vacuum gauge to hose. If no vacuum is present, go to step 4). If vacuum is present, disconnect 4-wire connector from control box. Check vacuum again on No. 16 hose. If vacuum is present, check vacuum hose routing.
    Fig 1: Testing EGR Valve (1.8L)
    G92D26214Courtesy of AMERICAN HONDA MOTOR CO., INC.
  3. If routing is okay, replace EGR control solenoid valve. If vacuum is not present, turn ignition off. Remove connector "A" from ECU. Using an ohmmeter, check for continuity between Red wire terminal of 4-wire connector and ground. If continuity is present, repair short in Red wire between EGR control solenoid valve and ECU connector terminal No. 11. If continuity is not present, substitute a known good ECU. If system operates properly, replace original ECU.
  4. If vacuum is not present during first vacuum test in step 2), install vacuum pump on EGR valve. With engine idling, apply 8 in. Hg to EGR valve. If engine does not stall/run rough and EGR valve does not hold vacuum, replace EGR valve.
  5. If engine stalls/runs rough and EGR valve holds vacuum, disconnect 4-wire connector from control box. Measure voltage between Black/Yellow wire terminal and body ground. If battery voltage is not present, repair open in Black/Yellow wire between solenoid valve and fuse No. 24.
  6. If battery voltage is present, install "T" fitting into No. 16 vacuum hose. See Fig 1 . Attach vacuum gauge to "T" fitting. Start engine and allow to idle. Connect battery voltage to terminal "B" at control box. See Fig 2 . While observing vacuum gauge, connect terminal "D" to negative battery terminal.
    Fig 2: Control Box Connector Terminal ID (1.8L)
    G92E26215Courtesy of AMERICAN HONDA MOTOR CO., INC.
  7. If gauge reads 8 in. Hg within one minute, go to step 9). If gauge does not read 8 in. Hg within one minute, turn ignition off. Inspect EGR vacuum hoses for leaks, restrictions and misrouting. Repair as necessary. If hoses are okay, disconnect lower hose on EGR control solenoid valve.
  8. Connect vacuum gauge to hose. Start engine, and allow to idle. If 6-10 in. Hg is not present, replace Constant Vacuum Control (CVC) valve. See Fig 3 . If 6-10 in. Hg is present, replace EGR control solenoid valve. See Fig 3 .
    Fig 3: Testing EGR Control Solenoid Valve & CVC Valve (1.8L)
    G92F26216Courtesy of AMERICAN HONDA MOTOR CO., INC.
  9. If gauge reads 8 in. Hg in step 7), turn ignition off. Ensure EGR control solenoid valve 2-wire connector is attached. Disconnect 3-wire from EGR valve. Turn ignition on. Measure voltage between Yellow/White (+) wire terminal and Green/White wire terminal. If about 5 volts are not present, go to step 12). If 5 volts are present, go to step 10).
  10. Turn ignition off. Connect 3-wire connector to EGR valve. Connect ECU Test Harness (07LAJ-PT3010A ) between ECU and ECU connector. See Figure . Measure voltage between test terminals D12 (+) and D22 (-). If 1.2 volts are present, observe voltmeter, and apply 8 in. Hg to EGR valve. Voltage should increase to about 4.3 volts. If voltage is correct, go to step 11). If voltage is not correct, repair open or short in Yellow wire between EGR valve and ECU connector terminal D12.
  11. If voltage does not consistently increase and decrease as vacuum increases and decreases, replace EGR valve. If voltage does increase and decrease with vacuum, reconnect No. 16 hose to EGR valve. Start engine and allow to idle. Measure voltage between test terminals A11 and A26. See Figure . If engine does not stall, repair open in Red wire between ECU connector terminal A11 and EGR control solenoid valve. If engine stalls, substitute a known good ECU. If symptom/condition goes away, replace original ECU.
  12. With 3-wire connector removed from EGR valve, measure voltage between Yellow/White wire terminal and body ground. If about 5 volts are present, repair open in Green/White wire between EGR valve and ECU connector terminal No. D22. If 5 volts are not present, connect "D" connector of ECU Test Harness (07LAJ-PT3010A ) to ECU, leaving vehicle wiring harness disconnected.
  13. Turn ignition on. Measure voltage between test terminals D20 (+) and D22 (-). If about 5 volts are present, repair open in Yellow/White wire between EGR valve and ECU connector terminal No. D20. If 5 volts are not present, substitute a known good ECU. If symptom/condition goes away, replace original ECU.
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