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Chart C-7 EGR System Check:

EGR System Wiring Circuit:

CIRCUIT DESCRIPTION:
The Exhaust Gas Recirculation (EGR) valve is controlled by a normally closed solenoid valve. The PCM turns the solenoid "ON" to allow vacuum to pass to the EGR, and turns the solenoid "OFF" to prevent EGR operation.

The duty cycle is calculated by the PCM based on information from the Engine Coolant Temperature (ECT) sensor, Throttle Position (TP) sensor, Manifold Absolute Pressure (MAP) sensor and engine speed. There should be no EGR when TP sensor input is below 3% or over 50% throttle, low vacuum or low engine coolant temperature.

With the ignition "ON" and engine "OFF," the EGR solenoid valve is de-energized. The solenoid valve, however, should be energized if the diagnostic "test" terminal is grounded with the ignition "ON" and engine "OFF."

CHART 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 shop rag or suitable stopper. Leaving the intake side hole open, attempt to start the engine. If the engine runs at a very high idle (up to 3000 RPM is possible) or starts and stalls, the EGR passages are not restricted. If the engine starts and idles normally, the EGR intake side passage in the intake manifold 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 in the intake manifold is restricted.
2. The vacuum at the gauge 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 grounded, the vacuum gauge should bleed off through a vent in the solenoid valve. The 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 valve is at fault.

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.