Code 12 - EGR System
- Warm engine to normal operating temperature (cooling fan on). Check harness and connections between EGR control solenoid and ECU. Verify vacuum supply to EGR control solenoid. Disconnect vacuum hose from EGR valve. Connect vacuum pump to EGR valve and apply vacuum.
- EGR valve should hold vacuum and engine should stall. If not, clean blocked EGR passage or replace EGR valve. If EGR held vacuum and engine stalled, turn ignition off. Disconnect vacuum hose from "T" connector to control box. Connect vacuum gauge. Restart engine. Manifold vacuum should be present. If not, repair blockage at port or hose.
- If vacuum reading is okay, reconnect hoses. Open emission control box and disconnect vacuum hose between air chamber and EGR control solenoid. Connect vacuum gauge. If 8 in. Hg is present, go to step 4). If not, replace Constant Vacuum Control (CVC) valve.
- Reconnect vacuum hose. Connect vacuum gauge to EGR control solenoid valve vacuum hose. If vacuum is present, replace EGR control solenoid valve or repair short in Red wire between ECU terminal A10 and EGR control solenoid valve.
- If no vacuum is present from step 4), disconnect 6-wire connector at emission control box. See Fig 1
. Connect jumper from battery positive to Black/Yellow terminal and negative jumper to Red terminal. If 8 in. Hg is now present, go to step 6). If not, replace EGR control solenoid valve.
- Measure voltage between Black/Yellow (pos.) terminal and ground. If battery voltage is present, go to next step. If not, repair open in Black/Yellow wire between the solenoid valve and fuel pump fuse.
- Turn ignition off. Connect 3-wire test harness between EGR valve lift sensor and sensor wire harness. Turn ignition on. Measure voltage between Red (pos.) and Green (neg.) test terminals. If 5 volts is present, go to next step. If not, go to step 11.
- Measure voltage between test harness White (pos.) and Green (neg.) terminals. If about one volt is present, go to next step. If not, replace EGR valve or repair short in Yellow wire between ECU terminal C8 and EGR valve lift sensor.
- Turn ignition off. Connect ECU test harness between ECU and ECU harness connector. Turn ignition on. Measure voltage between ECU terminals C8 and C14. See Figure
. If about one volt is present, go to next step. If not, repair open in White/Green wire between ECU terminal C8 and sensor.
- Disconnect test harness connector "A" from ECU side only. Measure voltage between harness terminals A10 and A18. If battery voltage is present, substitute a good known ECU. If condition is rectified, replace original ECU. If battery voltage is not present, repair open in White wire between ECU terminal A10 and EGR control solenoid valve.
- If from step 7), 5 volts was not present between Red and Green test harness terminals, measure voltage between Red (pos.) terminal and ground. If 5 volts is not present, go to next step. If 5 volts were present, repair open in Green/White wire between ECU terminal C14 and EGR lift sensor.
- Turn ignition off. Connect ECU test harness between ECU and ECU connector. Turn ignition on. Measure voltage between terminals C13 and C14. If about 5 volts is present, repair open in Yellow/White wire between ECU terminal C13 and sensor. If not, substitute a known good ECU. If specified voltage is now present, replace original ECU.
Courtesy of AMERICAN HONDA MOTOR CO., INC.