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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 no change in engine operating conditions is indicated, a DTC 32 will set.

The difference in long term fuel trim values between the idle (closed throttle) cell and cell 2 is used to monitor EGR system performance. When the difference between the two long term Fuel trim values is greater than about 15 and the long term fuel trim value in cell 2 is greater than 135 for 80 seconds or more, DTC 32 is set. The system operates in long term fuel trim cell 2 during a cruise condition at approximately 55 mph.

TEST DESCRIPTION: Number(s) below refer to circled number(s) on the diagnostic chart.

1. Intake Passage: Shut "OFF" engine and remove the EGR valve from the manifold. Plug the exhaust side hole with a suitable stopper. Leaving the intake side hole open, attempt to start the engine. If the engine runs at a high idle (up to 3000 RPM is possible) or starts and stalls, the EGR intake passage is not restricted. If the engine starts and idles normally, the EGR intake passage is restricted.

Exhaust Passage: With EGR valve still removed, plug the intake side hole with a suitable stopper. With the exhaust side hole open, check for the presence of exhaust gas. If no exhaust gas is present, the EGR exhaust side passage is restricted.

2. By grounding the diagnostic "test" terminal, the EGR solenoid should be energized and allow vacuum to be applied to the gauge. The vacuum at the gage may or may not slowly bleed off. It is important that the gauge is able to read the amount of vacuum being applied.

3. When the diagnostic "test" terminal is ungrounded, the vacuum gauge should bleed off completely through a vent in the solenoid. The vacuum pump gauge may or may not bleed off but this does not indicate a problem.

4. This test will determine if the electrical control part of the system is at fault or if the connector or solenoid is at fault.

5. At this point, it has been determined that the EGR solenoid, the ECM and the vacuum supply are OK.

DIAGNOSTIC AIDS:
Vacuum lines should be thoroughly checked for proper routing. Refer to "Vehicle Emission Control Information" label.

The DTC 32 chart is a functional check of the EGR system. If the EGR system works properly but a DTC 32 has been set, check other items that could result in high block learn values during a cruise condition at approximately 55 mph. Low fuel pressure or lean fuel injector(s) may set a DTC 32. It may be necessary to monitor fuel pressure while driving the vehicle at various road speeds and/or loads. Related Tests, Information and Procedures