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Code 12: EGR System

  1. Turn ignition off. Remove ACG (No. 15, 7.5-amp) from fuse in underdash fuse box for 10 seconds to reset ECM. Warm engine until cooling fan comes on. Road test vehicle about 10 minutes, keeping engine speed about 1700-2500 RPM. Check for fault codes. If Code 12 is not present, problem is intermittent. Check for poor connections at ECM, EGR valve, control box and shock tower wiring harness connectors.
  2. Test drive vehicle and retest. If Code 12 is present, start engine. Disconnect No. 11 hose from EGR valve. See Fig 1 . Start engine. 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. 11 hose. If vacuum is present, check vacuum hose routing. If routing is okay, replace EGR control solenoid valve.
    Fig 1: Identifying EGR No. 11 Hose
    G92G26217Courtesy of AMERICAN HONDA MOTOR CO., INC.
  3. If vacuum is not present, turn ignition off. Remove connector "A" from ECM. Using an ohmmeter, check for continuity between White wire terminal of 4-pin connector and ground. If continuity is present, repair short in White 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 or run rough or EGR valve does not hold vacuum, replace EGR valve.
  5. If engine stalls or 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 FUEL PUMP fuse (No. 22, 20-amp) in underdash fuse box.
  6. If battery voltage is present, install "T" fitting into No. 11 hose. Attach vacuum gauge to "T" fitting. Start engine, and allow it to idle. Connect battery voltage to terminal "A" of control box connector. See Fig 2 . While observing vacuum gauge, connect terminal "B" to negative battery terminal.
  7. If gauge reads 6 in. Hg within one second, go to step 9. If gauge does not read 6 in. Hg within one second, turn ignition off. Inspect 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. See Figure . Start engine, and allow it to idle. If 4.8-6.8 in. Hg is not present, replace Constant Vacuum Control (CVC) valve. See Fig 3 . If 4.8-6.8 in. Hg is present, replace EGR control solenoid valve. See Fig 3 .
    Fig 2: Identifying Control Box Connector Terminals
    G91B16288Courtesy of AMERICAN HONDA MOTOR CO., INC.
    Fig 3: EGR Control Solenoid Valve & Constant Vacuum Control Valve
    G92I26219Courtesy of AMERICAN HONDA MOTOR CO., INC.
  9. If gauge read 6 in. Hg in step 7, turn ignition off. Reconnect 4-pin connector at control box. Disconnect EGR valve position sensor. Turn ignition on. Measure voltage between Yellow/White (+) and Green/White (-) wires. If about 5 volts are present, go to step 12.
  10. If voltage is not about 5 volts, measure voltage between Yellow/White wire (+) and body ground. If about 5 volts are present, repair open in Green/White wire between EGR valve lift sensor and ECM connector D22. If voltage is not about 5 volts, turn ignition off.
  11. Connect ECM Test Harness (07LAJ-PT3010A ) connector "D" to ECM, leaving vehicle wiring harness disconnected. Turn ignition on. Measure voltage between test terminals D20 (+) and D22 (-). See Figure . If voltage is about 5 volts, repair open in Yellow/White wire between ECM connector terminal D20 and EGR valve lift sensor. If voltage is not about 5 volts, replace ECM and retest.
  12. If voltage was about 5 volts in step 9, turn ignition off and reconnect 3-pin connector at EGR valve lift sensor. Connect ECM Test Harness (07LAJ-PT3010A ) between ECM and ECM connectors. See Figure . Turn ignition on. Measure voltage between test terminals D12 (+) and D22 (-). Voltage should be 1.2 volts with no vacuum and 4.3 volts with 6 in. Hg vacuum applied to EGR valve. If voltage is not as specified, repair open or short in Black/White wire between EGR valve lift sensor and ECM connector terminal D12.
  13. If voltage is as specified, check if it consistently increases and decreases as vacuum increases and decreases. If vacuum does not consistently increase and decrease as vacuum increases and decreases, replace EGR valve. If voltage increases and decreases with vacuum, reconnect No. 11 hose. Start engine. Allow it to idle. Connect jumper wire between test terminals A11 and A26. See Figure .
  14. If engine does not stall or run rough, repair open in White wire between ECM connector terminal A11 and EGR control solenoid valve. If engine stalls or runs rough, replace ECM and retest.
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