Chart C-7 Exhaust Gas Recirculation (EGR) System Check

Chart C-7 (1 Of 2):

Exhaust Gas Recirculation (EGR) Circuit:

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

The duty cycle is calculated by the Powertrain Control Module (PCM) based on information from the Engine Coolant Temperature (ECT), Intake Air Temperature (IAT), Throttle Position (TP) sensor, and Manifold Absolute Pressure (MAP) sensors. Also, engine RPM and the P/N Position (PNP) switch input affect EGR. There should be no EGR when in park or neutral, TP sensor below a calibrated value (manual transmission), or TP sensor indicating Wide Open Throttle (WOT).

With the ignition "ON" and engine "OFF," the EGR solenoid valve is de-energized. The solenoid valve, however, should be energized, if the output/field service enable 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 output/field service enable terminal is grounded, or Tech 1 (or equivalent) Scanner is used, 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.

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.

When the transmission enables Transmission Control Clutch (TCC), the EGR will be in a reduced duty cycle.

Chart C-7 (2 of 2):

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

1. The remaining test checks the ability of the EGR valve to interact with the exhaust system. This system uses a negative backpressure EGR valve which should hold vacuum with engine "OFF."
2. When engine is started, exhaust backpressure at the base of the EGR valve should open the valve's internal bleed and vent the applied vacuum allowing the valve to seat.

DIAGNOSTIC AIDS
Suction from shop exhaust hoses can alter backpressure and may affect the functional check of the EGR valve.

During normal EGR valve operation, the movement of the EGR pintle is small. It is important to determine whether the valve pintle moves and not how much it moves.

When the transmission enables TCC the EGR will be in a reduced duty cycle.