Exhaust Gas Recirculation (Port Fuel Injection)

Chart C-7B - Exhaust Gas Recirculation (EGR) Check:

Wiring Diagram for Chart C-7B - Exhaust Gas Recirculation (EGR) Check:

CHART C-7B - EXHAUST GAS RECIRCULATION (EGR) CHECK

Circuit Description:


The Exhaust Gas Recirculation (EGR) valve is controlled by a normally open, pulse width modulated (PWM) solenoid. The ECM turns the solenoid "OFF" to allow vacuum to pass to the EGR and turns the solenoid "ON" to prohibit EGR operation. When EGR is commanded, the solenoid is turned "ON" and "OFF" many times a second (duty cycle).

The duty cycle is calculated by the ECM based on information from the coolant, MAT, TPS, and MAF sensors. Also, engine rpm's and the P/N switch input affect EGR. There should be no EGR when in park or neutral, TPS below a calibrated value or TPS indicating WOT.

With the ignition "ON" and engine stopped, the EGR solenoid is de-energized. The solenoid, however, should be energized if the diagnostic terminal is grounded with the ignition "ON" and engine not running.


Test Description: Numbers below refer to circled numbers on the diagnostic chart.

1. This will test the solenoid value to determine if it is capable of closing off the manifold vacuum from the EGR valve. The vacuum may bleed off slowly but this should not be considered a fault.

2. As soon as back pressure is available at the EGR valve, the bleed portion in the valve should open and cause the valve to go to its heated position.

3. To check P/N switch:


^ Connect a test light between EGR solenoid harness terminals.

^ Engine at normal operating temperature.

^ Accelerate engine to about 1500 rpm's in park (observe light, it should stay "ON").

^ Repeat test in drive and the test light should go dim or out.

^ If both conditions are met, then the P/N switch is OK, otherwise see CHART C-1A.