By-Pass Control Solenoid Valves
- Check by-pass valve shaft for binding, sticking and smooth movement. If necessary, clean linkage and shafts with carburetor cleaner.
- Start engine, and allow to idle. Remove vacuum hose No. 2 from by-pass low control diaphragm and attach a vacuum gauge to hose. See Fig 1
. Check for vacuum. If vacuum is present, go to step 4).
Courtesy of AMERICAN HONDA MOTOR CO., INC.
- If vacuum is not present, remove vacuum hose No. 4 at by-pass low control solenoid, and check for vacuum. If vacuum is present, go to step 7). If vacuum is not present, check vacuum line between solenoid and intake manifold. Repair as necessary, and recheck.
- Disconnect vacuum hose No. 8 from by-pass high control diaphragm. Attach vacuum gauge to vacuum hose No. 8, and check for vacuum at idle. If vacuum is not present, go to step 11). If vacuum is present, raise engine speed to 3300 RPM and check vacuum gauge. Check for vacuum at vacuum hose No. 2.
- If vacuum is present, go to step 16). If no vacuum is present, raise engine speed to 4000 RPM and check for vacuum at vacuum hose No. 8. If vacuum is not present, system is okay. If vacuum is present, go to next step.
- Disconnect by-pass high control solenoid 6-wire connector, and recheck for vacuum. See Fig 2
. If vacuum exists, replace by-pass high control solenoid valve. If vacuum is not present, check for short or open in Yellow wire between ECU terminal A18 and solenoid 6-wire connector. If wire is okay, substitute a known good ECU, and retest. If problem is corrected, replace ECU.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
- Disconnect 6-wire connector from by-pass low control solenoid. Measure voltage between Black/Yellow (positive) and Red/Blue (negative) wire terminals. If battery voltage is present, replace by-pass low control solenoid valve. If voltage is not present, go to next step.
- Measure voltage between Black/Yellow wire terminal and body ground. If battery voltage is not present, repair open in Black/Yellow wire between solenoid 6-wire connector and fuse No. 22.
- If battery voltage is present, turn ignition off. Attach PGM-FI test harness connector between ECU and ECU harness connector. Check continuity of Red/Blue wire between ECU terminal A14 and solenoid 6-wire connector.
- If continuity is not present, repair open in Red/Blue wire. If continuity is present, substitute a known good ECU, and retest. If symptom goes away, replace ECU.
- Remove vacuum hose No. 4 at by-pass high control solenoid, and check for vacuum. If vacuum is present, go to next step. If vacuum is not present, check vacuum line between solenoid and intake manifold. Repair as necessary, and recheck.
- Disconnect solenoid 6-wire connector. Measure voltage between Black/Yellow (positive) and Yellow (negative) wire terminals. If battery voltage is present, replace by-pass high control solenoid valve. If voltage is not present, go to next step.
- Measure voltage between Black/Yellow wire terminal and body ground. If battery voltage is NOT present, repair open in Black/Yellow wire between solenoid 6-wire connector and fuse No. 22.
- If battery voltage is present, turn ignition off. Attach PGM-FI test harness connector between ECU and ECU harness connector. Check continuity of Yellow wire between ECU terminal A18 and solenoid 6-wire connector.
- If continuity is not present, repair open in Yellow wire. If continuity is present, substitute a known good ECU, and retest. If symptom goes away, replace ECU.
- Disconnect by-pass low control solenoid 6-wire connector, and recheck for vacuum. If vacuum exists, replace by-pass low control solenoid valve. If vacuum is not present, check for short or open in Red/Blue wire between ECU terminal A14 and solenoid 6-wire connector. If wire is okay, substitute a known good ECU, and retest. If problem is corrected, replace ECU.