Hot Engine
- Disconnect vacuum hose from EGR valve and connect vacuum gauge to hose. Connect voltmeter positive probe into the terminal at the control box connector (Yellow/White wire). Connect the negative probe to ground.
- Start and warm-up engine to normal operating temperature (cooling fan must come on). Test EGR system under the following engine operating conditions. Check vacuum and voltage specifications.
EGR SYSTEM TEST
| Engine Condition |
EGR Valve Vacuum |
Yellow/White Wire Voltage |
| 1 Idle |
None |
Yes |
| 2 Hard Accel. |
2-6 in. Hg |
None |
| 3 4500 RPM |
2-6 in. Hg |
None |
| 4 Deceleration |
None |
Yes |
- If vacuum is present in condition No. 1 or no vacuum available for condition No. 2 and No. 3, check vacuum hose routing. If there are no defects, replace the EGR control valves A and B.
- If no voltage is present for condition No. 1 or No. 4, or there is voltage for condition No. 2 or No. 3, check thermosensor and vacuum switch C. Check for voltage at control unit connector (Black/Yellow wire) with ignition on. There should be voltage. If there is no voltage, check wiring.
- Check Brown/Black wire for continuity between control unit and ground. Wire should have continuity. If vacuum is available for condition No. 4, replace EGR solenoid valve A. Retest system.