Exhaust Gas Recirculation: Testing and Inspection

This test assumes no diagnostic trouble code (DTC) 34 or 32 is stored.

Circuit Description:
The EGR valve is controlled by a normally closed solenoid (allow a vacuum to pass when energized). The Engine Control Module (ECM) pulses the solenoid to turn "ON" and regulate the EGR. The ECM diagnoses the system using an internal EGR test procedure.
The ECM control of the EGR is based on the following inputs:
- Engine coolant temperature - above 25°C.
- Throttle Position Sensor - "OFF" idle
- Manifold absolute pressure
If Diagnostic Trouble Code (DTC) 24 is stored, use that chart first.
DTC 32 will detect a faulty solenoid, vacuum supply, EGR valve or plugged passage. This chart checks for plugged EGR passages, a sticking EGR valve, or a stuck open or inoperative solenoid.

Test Description:
Number(s) below refer to circled number(s) on the diagnostic chart.
1. With the ignition "ON", engine stopped, the solenoid should not be energized and vacuum should not pass the EGR valve.
2. Grounding the diagnostic terminal will energize the solenoid and allow vacuum to pass to valve.
3. Checks for plugged EGR passages. If passages are plugged, the engine may have severe detonation on acceleration.
4. The EGR solenoid will not be energized in park or neutral. This test will determine if the switch input is being received by the ECM.





CHART C-7