Part 2 of 3

DTC 32 Chart Part 2 Of 3:

Wiring Diagram:

MAP With Key On Engine Off:

CIRCUIT DESCRIPTION:

The ECM operates a solenoid valve to control the Exhaust Gas Recirculation (EGR) valve. This solenoid valve is normally closed. By providing a ground path, the ECM energizes the solenoid valve which then allows vacuum to pass to the EGR valve.

The ECM monitors EGR effectiveness by de-energizing the EGR control solenoid valve, thereby, shutting "OFF" vacuum to the EGR valve diaphragm. With the EGR valve closed, manifold vacuum will be greater than it was during normal EGR operation and this change will be relayed to the ECM by the MAP sensor. If the vacuum change is not within the calibrated window, a DTC 32 will be set.

The ECM will check EGR operation when:

^ Vehicle speed is above 80 km/h (50 mph).
^ MAP is as listed in table (depends on altitude).
^ TP is between 9% and 20% (5.OL & 5.7L).
^ TP is between 5% and 20% (4.3L).
^ No change in Throttle Position (TP) while test is being run.

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


6. The remaining tests check the ability of the EGR to interact with the exhaust system. This system uses a POSITIVE BACKPRESSURE EGR VALVE which will not hold vacuum until sufficient exhaust backpressure is at the base of the valve.

7. The EGR valve diaphragm should move when sufficient exhaust backpressure is present at the base of the EGR valve and when vacuum is applied to the valve. Rapidly snapping the throttle from idle should provide sufficient exhaust back pressure to the base of the EGR valve, which will close an internal vacuum bleed.

With the EGR valve's internal vacuum bleed closed, the jumpered vacuum supply can now lift the valve off its seat.

8. Excessive exhaust back pressure from bent or restricted exhaust system components could provide enough back pressure to the base of the EGR valve to close the EGR valve's internal vacuum bleed. This would allow undesired EGR valve operation at idle.

9. A Plugged EGR exhaust passage can stop exhaust back pressure from reaching the base of the EGR valve. If this takes place, the EGR valve's internal vacuum bleed may remain open, and prevent vacuum from operating the EGR valve.