Exhaust Gas Recirculation: Testing and Inspection

EGR Diagnosis:

DFI Emission Circuit:

DIAGNOSIS Numbers below refer to circled numbers on the diagnostic chart.

1. Checking for EGR valve's ability to flow sufficient exhaust gas to engine. RPM should drop and idle should become rough or stall. Compare the RPM drop to a known good car.

2. Checking for blocked EGR passages in the intake manifold.

3. Checking for EGR solenoid able to pass vacuum.

4. Checking for voltage to EGR solenoid and ground signal from the ECM. If either of these is missing, the EGR solenoid will command EGR on at all times.

5. Checking for ECM ability to turn solenoid off. If the light goes off, the electrical portion of the EGR system is OK.

TEST DESCRIPTION

This engine uses a positive backpressure EGR valve which limits EGR flow with low exhaust backpressure (idle, decel, etc.). It is very important that exhaust tubes which decrease backpressure (pull air through) are not hooked to the vehicle when diagnosing the EGR system.

^ Check 10 amp ECS fuse (#5) on fuse panel.

^ Measure EGR solenoid resistance. Refer to "SPECIFICATIONS". Conect a vacuum gauge to the source side of the EGR solenoid. Start the engine, manifold vacuum should be present. If it is not, repair leaks or obstruction between the EGR solenoid and throttle body.

^ Check vacuum supply hoses for leaks, restrictions, and obstructions. Clean out or replace as necessary.

^ Check intake manifold passages for any obstructions that would prevent exhaust gases from passing through.

^ Connect a vacuum gauge to the EGR valve vacuum supply. There should be no vacuum with the engine idling. If there is, follow chart C-7 above. With the gauge hooked to the EGR valve vacuum supply, disconnect the EGR solenoid connector. There should be more than 8 inches of vacuum available. If not, repair leak or obstruction in EGR valve vacuum hose.