Hot Engine

Disconnect and plug lower air suction hose from anti-afterburn valve. Remove air cleaner cover and filter. Raise and support front of vehicle. Set parking brake and block rear wheels.
Place shift lever in second position (selector lever in "2" position for auto. trans.) and accelerate above 15 MPH. Quickly release throttle and check for bubbling noise. If bubbling noise is heard, system is okay.
If bubbling noise is not heard, check for voltage at air suction control solenoid valve (Yellow/Green wire). If voltage is not present, turn ignition on and check for voltage at control unit connector (Blue wire). Voltage should be present.
If voltage is not present, check Blue wire between ignition coil and control unit. Check speed sensor, thermosensor, intake air temperature sensor, vacuum switch A and vacuum switch C. Turn ignition on and check for voltage at control unit connector (Black/Yellow wire).
If there is no voltage, check wiring. Check Brown/Black wire for continuity between control unit and ground. Continuity should be present.
If there is voltage, disconnect vacuum hose No. 5 from air suction cut-off diaphragm. Check for disconnected or leaking vacuum hoses. If okay, replace air suction cut-off diaphragm valve and retest. If vacuum is present, replace air suction cut-off diaphragm and retest.