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Code 12: EGR System (1.8L A/T)

  1. Turn ignition off. Remove BACK-UP fuse (7.5-amp) from underhood fuse/relay box for 10 seconds to reset ECM. Warm engine until cooling fan comes on. Road test vehicle for about 10 minutes, keeping engine speed about 1700-2500 RPM. Check ECM for fault codes. If Code 12 is not present, problem is intermittent. Check ECM, EGR valve and shock tower wiring harness connectors for poor connections.
  2. Test drive vehicle and retest. If Code 12 is present, start engine. Disconnect 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-pin connector from control box, located on right side of firewall. Check vacuum again on No. 16 hose. If vacuum is present, check vacuum hose routing.
    Fig 1: Testing EGR Valve 1.8L A/T)
    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 ECM. Using an ohmmeter, check for continuity between Red wire terminal of 4-pin connector and ground. If continuity is present, repair short in Red wire between EGR control solenoid valve and ECM connector terminal A11. If continuity is not present, replace ECM and retest.
  4. If vacuum was 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 or EGR valve does not hold vacuum, replace EGR valve.
  5. If engine stalls/runs rough and EGR valve holds vacuum, disconnect 4-pin 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 (15-amp) in underdash fuse/relay box.
  6. If battery voltage is present, install "T" fitting into No. 16 hose. See Fig 1 . Attach vacuum gauge to "T" fitting. Start engine, and allow it 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.
  7. If gauge reads 8 in. Hg within one second, go to step 9. If gauge does not read 8 in. Hg within one second, 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 it 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 2: Identifying Control Box Connector Terminals (1.8L A/T)
    G92E26215Courtesy of AMERICAN HONDA MOTOR CO., INC.
    Fig 3: EGR Control Solenoid Valve & Constant Vacuum Control Valve
    G92F26216Courtesy of AMERICAN HONDA MOTOR CO., INC.
  9. If gauge read 8 in. Hg in step 7, turn ignition off. Ensure EGR control solenoid valve 2-pin connector is attached. Disconnect 3-pin connector from EGR valve lift sensor. Turn ignition on. Measure voltage between Yellow/White (+) and Green/White (-) wire terminals. If voltage is not about 5 volts, go to step 12. If voltage is about 5 volts, go to step 10.
  10. Turn ignition off. Connect 3-pin connector to EGR valve lift sensor. Connect ECM Test Harness (07LAJ-PT3010A ) between ECM and ECM connectors. 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 ECM connector terminal D12.
  11. If voltage does not consistently increase and decrease as vacuum increases and decreases, replace EGR valve. If voltage consistently increases and decreases with vacuum, reconnect No. 16 hose to EGR valve. Start engine, and allow it to idle. Connect a jumper wire between test terminals A11 and A26. See Figure . If engine does not stall or run rough, repair open in Red wire between ECM connector terminal A11 and EGR control solenoid valve. If engine stalls or runs rough, replace ECM and retest.
  12. With 3-pin 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 ECM connector terminal No. D22. If voltage is not 5 volts, connect connector "D" of ECM Test Harness (07LAJ-PT3010A ) to ECM, 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 ECM connector terminal No. D20. If voltage is not about 5 volts, replace ECM and retest.
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