Part 2 of 2

Code Chart 32:

EGR Solenoid Circuit:

CIRCUIT DESCRIPTION:
The Exhaust Gas Recirculation (EGR) system is controlled by the ECM. The ECM controls the vacuum being supplied to the valve by energizing and de-energizing a solenoid. The ECM uses information from various engine sensors to determine when EGR is necessary. Once the ECM has requested EGR by grounding the solenoid circuit, the ECM will monitor engine operating conditions to determine if exhaust gas flow has entered the intake manifold. When the ECM tests for EGR operation and not change in engine operating conditions is indicated, a Code 32 will set.

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

1. The remaining tests check the ability of the EGR valve 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.

2. The EGR valve diaphragm should move when sufficient exhaust backpressure is present at the base of the valve and when vacuum is being supplied to the valve. Rapidly snapping the throttle from idle should provide sufficient exhaust backpressure to the base of the 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. The amount of valve pintle movement will be small. It is important that the valve pintle moves at the proper time.

3. Excessive exhaust backpressure from bent or restricted exhaust system components could provide enough backpressure at the base of the EGR valve to close the valve's internal bleed and allow undesired EGR valve operation at idle.

4. Plugged EGR exhaust passages can block exhaust backpressure from reaching the EGR valve. With no EGR exhaust backpressure at the base of the valve, the valve's internal bleed will remain open and prevent vacuum from operating the valve.


DIAGNOSTIC AIDS:
Vacuum lines should be thoroughly checked for proper routing. Refer to vehicle emission control information label. Suction from shop exhaust hoses can alter backpressure and may affect the functional check of the EGR valve.

If the EGR system is found to be functioning correctly and Code 32 is set, low fuel pressure or lean fuel injectors could be the cause of setting Code 32. Chart C-2A Fuel Injector Balance Test