System Diagnosis

COLD ENGINE

1. Ensure that coolant temperature is below 122 deg. F.
2. Disconnect vacuum hose No. 16 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, perform hot engine test.
5. If there is vacuum, check for voltage at yellow/white wire at EGR control solenoid valve A.
6. If there is voltage, replace EGR control solenoid valve A and repeat test.
7. If there was no voltage in step 5, refer to appropriate troubleshooting condition.

HOT ENGINE

1. Disconnect vacuum hose No. 16 from EGR valve and connect vacuum gauge to hose.
2. Push voltmeter positive probe into pink (1983) or yellow/white (1984-86) terminal at connector of control box No. 1 and connect negative probe to suitable ground.
3. Raise and support front of vehicle, block rear wheels and apply hand brake.
4. Start engine and run until it reaches operating temperature.
5. Check that vacuum and voltage are as indicated, Figs. 68 and 69.
6. If readings are incorrect, refer to appropriate troubleshooting condition.