Resonator Control
- Start engine and allow to idle. Remove vacuum hose to resonator control diaphragm. Connect vacuum gauge. If vacuum is NOT present, go to step 3).
- If vacuum is present, increase engine speed to about 3800 RPM. Check vacuum gauge. If vacuum is still present, go to step 7). If vacuum is NOT present, connect vacuum pump/gauge to resonator diaphragm. See Fig 1
. Apply vacuum. If diaphragm linkage activates and vacuum holds, problem DOES NOT exists in resonator system. If linkage does not move and/or diaphragm does not hold vacuum, replace diaphragm or repair binding linkage.
- Disconnect lower vacuum-supply hose at resonator solenoid. Check for vacuum. If vacuum is NOT present, check for blockage in hose or vacuum port, or disconnected hose.
- If vacuum is present, disconnect 2-wire connector from resonator control solenoid (mounted on resonator housing). Measure voltage between Black/Yellow wire (positive) and Red/Blue wire (negative) terminals. If battery voltage is present, replace resonator control solenoid.
- If battery voltage is NOT present, measure voltage between ground and Black/Yellow wire. If battery voltage is NOT present, repair open in Black/Yellow wire between 2-wire connector and fuse No. 9 or replace fuse.
- If battery voltage is present, turn ignition off. Connect PGM-FI Test Harness connector between ECU and ECU connectors. Check continuity of Red/Blue wire between ECU terminal A14 and 2-wire resonator solenoid connector. If continuity does not exist, repair Red/Blue wire as necessary. If continuity does exist, substitute a known good ECU and retest. If condition goes away, replace original ECU.
- With engine speed at 3800 RPM, disconnect 2-wire resonator solenoid connector. If vacuum is present, replace solenoid. If vacuum is NOT present, turn ignition off. Disconnect 6-wire connector from ECU. See Figure
. Check Red/Blue wire of ECU terminal A14 for continuity to ground. If continuity exists, repair short to ground between ECU terminal A14 and 2-wire solenoid connector.
- If there is no continuity to ground, substitute a known good ECU and retest. If problem goes away, replace original ECU.
Courtesy of AMERICAN HONDA MOTOR CO., INC.