By-Pass Control System: Legend
- Check by-pass valve shaft for binding, sticking and smooth movement. Ensure by-pass valve is in close contact with stopper when by-pass valve is fully open. Ensure by-pass valve is in close contact with full close screw when by-pass valve is fully closed. See Fig 2
.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
- Clean linkage and shafts with carburetor cleaner if fault is found. Start engine and allow to idle. Remove No. 2 vacuum hose from by-pass control diaphragm and attach a vacuum gauge to hose. See Fig 1
. Check for vacuum. If vacuum is present, go to step 4).
- If no vacuum is present, remove No. 12 vacuum hose at solenoid and check for vacuum. If vacuum is present, proceed to step 7). If no vacuum is present, check vacuum line between solenoid and intake manifold. Repair as necessary and recheck.
- If vacuum was present in step 2), raise engine speed to 4000 RPM and check vacuum gauge. If vacuum is present, proceed to step 11). If no vacuum is present, connect No. 2 vacuum hose and disconnect No. 7 vacuum hose from by-pass control diaphragm. Attach vacuum gauge to No. 8 vacuum hose and check for vacuum at idle.
- If no vacuum is present, proceed to step 13). If vacuum is present, raise engine speed to 3500 RPM and check for vacuum at No. 7 hose. If no vacuum is present, system is okay. If vacuum is present, proceed to step 6).
- If vacuum is present at 3500 RPM, disconnect solenoid 6-wire connector and check again for vacuum. See Fig 3
. If vacuum is now present, check Green wire between ECU terminal B3 and solenoid 6-wire connector. If wire is okay, replace by-pass solenoid valve B. If no vacuum is present, substitute a known good ECU and retest. If symptom is rectified, replace original ECU.
- If vacuum was present in step 3), disconnect solenoid 6-wire connector. See Fig 3
. Measure voltage between Black/Yellow (pos.) and Red/Blue (neg.) terminals. If battery voltage is present, replace by-pass control solenoid valve A. If no voltage is present, go to next step.
- If no battery voltage was present in step 7), measure voltage between Black/Yellow terminal and body ground. If battery voltage is not present, repair open in Black/Yellow wire between 6-wire connector and No. 9 fuse.
- If battery voltage was present in step 8), turn ignition off. Attach System Checker Harness (07999-PD6000A) between ECU and ECU connector. Check for continuity between Red/Blue wire of solenoid connector and ECU terminal A14.
- If no continuity is present, repair open in Red/Blue wire between ECU and connector. If continuity is present, substitute a known good ECU and retest. If symptom is rectified, replace original ECU.
- If no vacuum is present in step 4), proceed to step 12). If vacuum was present in step 4), disconnect solenoid 6-wire connector. See Fig 3
. If vacuum is now present, check for short in Red/Blue wire between ECU terminal A14 and 6-wire connector. If wire is okay, replace by-pass control solenoid valve A.
- If no vacuum was present in step 11), substitute a known good ECU and retest. If symptom is rectified, replace original ECU.
- If no vacuum was present in step 5), disconnect solenoid 6-wire connector. See Fig 3
. Check for battery voltage between Black/Yellow (pos.) and Green (neg.) terminals. If battery voltage is present, replace by-pass control solenoid valve B. If no voltage is present, proceed to next step.
- Measure voltage between Black/Yellow terminal and body ground. If battery voltage is not present, repair open in Black/Yellow wire between 6-wire connector and fuse No. 9.
- If battery voltage is present, turn ignition off. Connect System Checker Harness (07999-PD6000A) between ECU and ECU connector. Check for continuity of Green wire terminal and ECU connector terminal B3. If no continuity is present, repair open in Green wire between ECU and connector.
- If continuity is present, substitute a known good ECU and retest. If symptom is rectified, replace original ECU.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Courtesy of AMERICAN HONDA MOTOR CO., INC.