Exhaust Gas Recirculation: Testing and Inspection

SYSTEM INSPECTION

NOTE: Troubleshoot with the Self-Diagnosis Checker before performing the following steps. Check the condition of the wiring harness and/or vacuum lines and connectors before checking the sensors or switches.


1. Check the vacuum hose routing.
2. If incorrect connection, clogging, or leakage is found, repair or replace the hose.
3. Warm up the engine and run it at idle.

Disconnecting EGR System:

4. Disconnect vacuum the hose from the EGR control valve and plug it.
5. Verify that the engine runs smoothly.
6. If it does not, check the EGR control valve.

Measuring EGR Vacuum:

7. Connect a vacuum gauge to the EGR hose.
8. Verify that the gauge shows no vacuum.
9. Accelerate the engine, and verify that the gauge shows vacuum.
10. Decelerate the engine, and verify that the gauge again shows no vacuum.
11. If a problem is found, check the duty solenoid valve and the "2L" and "2K" terminals of the engine control unit.

NOTE: The engine control unit is located behind the passenger kick panel.

Measuring EGR Vacuum:

12. Connect a vacuum gauge between the duty solenoid valve and the EGR control valve, as shown.
13. Accelerate the engine, and note the amount of vacuum.
14. Disconnect vacuum hose at the EGR valve and plug it.
15. Accelerate and verify that the gauge shows higher vacuum than in step 13.
16. If it does not, check the EGR position sensor, the "1F" terminal of the engine control unit, and the duty solenoid valve.

Jumpering Coolant Temperature Switch Harness:

17. Disconnect the connectors from the water temperature switch, and connect them with a jumper wire.
18. With vacuum hose "A" plugged, verify that the gauge shows no vacuum when the engine is accelerated.
19. If it shows vacuum, check the duty solenoid valve and the 1Q terminal of the engine control unit.