System Diagnosis

COLD ENGINE

1. Engine coolant temperature must be below set temperature of thermosensor and thermosensor must have continuity.
2. Disconnect vacuum hose from EGR valve and connect vacuum gauge to hose.
3. Start engine and raise engine speed to 4500-5000 RPM.
4. If vacuum is not available, proceed to hot engine inspection, except on 1981 models, for which you should proceed to step 8.
5. If there is vacuum, replace thermovalve C and repeat test for 1984 Civic or check for voltage at EGR control solenoid valve for models except 1984 Civic.
6. If there is voltage, replace EGR control solenoid valve and retest.
7. If there is no voltage, check thermosensor operation, wiring, and fuses, repair or replace as necessary and retest.

HOT ENGINE

1. Disconnect vacuum hose from EGR valve and connect vacuum gauge to hose.
2. On models except 1984 Accord, push voltmeter positive probe into blue/yellow (1982-83 Accord), blue (1982-83 Civic and Prelude), yellow/white (1984 Civic) wire terminal control box connector and connect negative probe to suitable ground.
3. On all models, raise and support front of vehicle, block rear wheels, and apply hand brake.
4. Start engine and allow it to reach normal operating temperature.
5. On 1982-84 Accord, remove control box by removing mounting bolts from fire wall, then remove control box cover by removing 4 attaching screws.
6. On all other models, check VACUUM/VOLTAGE CHARTS.
7. If readings are incorrect, refer to appropriate troubleshooting condition.