Turbo

Chart C-7:

Chart C-7 Wiring Diagram:

CIRCUIT DESCRIPTION:

The integrated electronic EGR valve functions similar to a standard EGR (ported vacuum) valve with a remote vacuum regulator. The internal solenoid is normally open (vacuum is vented to atmosphere when the ECM is not signalling the EGR). The EGR valve has a sealed cap. The solenoid valve opens and closes the vacuum signal, which varies the amount of vacuum vented to atmosphere and to the diaphragm. The electronic EGR valve contains a voltage regulator which converts the ECM signal to vary the amount of exhaust gas flow and current to the solenoid. The ECM controls exhaust gas flow with a pulse width modulated signal based on airflow, throttle position, and engine rpm.
This system also contains a pintle position sensor, similar to a TPS. As exhaust gas flow increases, the sensor output increases.


TEST DESCRIPTION: The numbers below refer to circled numbers on the diagnostic chart.

1. Whenever the solenoid is not powered, the solenoid valve should be open (the EGR diaphragm should NOT be moving). If the filter is plugged, the vacuum applied with a hand held pump will cause the diaphragm to move due to the vacuum not being allowed to vent.

2. This test determines if the EGR filter is plugged or if the EGR is at fault. Be careful removing the filter to avoid damage to the EGR assembly see MAINTENANCE PROCEDURES.

3. If the valve moves in this test, it is probably due to circuit 435 being shorted to ground.

4. Grounding the diagnostic terminal should energize the solenoid to close the vent, and allow the vacuum to move the EGR valve diaphragm.

5. The EGR assembly is designed to have some leakage and therefore seven inches (Hg) of vacuum is all that can be held on the assembly, but if a large leak exists, less than 3" Hg, the EGR assembly is leaking and needs to be replaced.



DIAGNOSTIC AIDS:

Some "Scan" tools will read EGR pintle position in volts. The EGR position voltage can be used to determine that the pintle is moving. When no EGR is commanded, the position sensor should read between 0.5 volt and 1.5 volts, and increase with the commanded EGR duty cycle.