Code 12: EGR System
- Turn ignition off. Remove BACK-UP fuse (10-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 for poor connections at ECM, control box, EGR valve position sensor and wire harness connectors. Test drive vehicle and retest.
- If Code 12 is present, start engine. Disconnect No. 1 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. Check vacuum again on No. 1 hose. If vacuum is present, check vacuum hose routing. If routing is okay, replace EGR control solenoid valve.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
- If vacuum is not present, turn ignition off. Remove connector "A" from ECM. Check for continuity between Red wire terminal of control box 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.
- If vacuum was not present during first vacuum test in step 2), install vacuum pump on EGR valve vacuum port. With engine idling, apply 6 in. Hg to EGR valve. If engine does not stall or run rough or EGR valve does not hold vacuum, replace EGR valve.
- If engine stalls or runs rough and EGR valve holds vacuum, turn ignition off and disconnect 4-pin connector from control box, located on firewall, behind intake manifold. Turn ignition on. 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 ECM fuse (No. 2, 15-amp) located in underdash fuse box. If battery voltage is present, install "T" fitting into No. 1 hose.
- Attach vacuum gauge to "T" fitting. Start engine, and allow it to idle. Connect battery voltage to terminal "B" of 4-pin connector. See Fig 2
. While observing vacuum gauge, connect terminal "D" to negative battery terminal.
- 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 EGR hoses for leaks, restrictions and misrouting. Repair as necessary. If hoses are okay, disconnect lower hose on EGR control solenoid valve.
- Connect vacuum gauge to disconnected hose. Start engine, and allow it to idle. If about 6 in. Hg is not present, replace Constant Vacuum Control (CVC) valve. See Fig 3
. If about 6 in. Hg is present, replace EGR control solenoid valve. See Fig 3
.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
- If gauge read 6 in. Hg in step 7), turn ignition off. Reconnect 4-pin connector to control box. Disconnect 3-pin connector to 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, proceed to step 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
. Turn ignition on. Measure voltage between test terminals D12 (+) and D22 (-). Voltage should be about 1.2 volts with no vacuum and about 4.3 volts with 6 in. Hg vacuum applied to EGR valve. If voltage is correct, go to step 11). If voltage is incorrect, repair open or short in White/Black wire between EGR valve lift sensor and ECM connector terminal D12.
- Check if voltage consistently increases and decreases as vacuum increases and decreases. If voltage does not consistently increase and decrease with vacuum, replace EGR valve. If voltage increases and decreases with vacuum, reconnect No. 1 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.
- If about 5 volts were not present in step 9), measure voltage between Yellow/White wire terminal of EGR valve position sensor 3-pin connector and body ground. If about 5 volts are present, repair open in Green/White wire between EGR valve lift sensor and ECM connector terminal D22. If voltage is not about 5 volts, connect connector "D" of ECM Test Harness (07LAJ-PT3010A
) to ECM, leaving vehicle wiring harness disconnected.
- 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.