Exhaust Gas Recirculation (EGR) System Check

Chart C-7:

EGR Wiring Diagram:

EGR SYSTEM CHECK

CIRCUIT DESCRIPTION:

The digital EGR valve is designed to accurately supply exhaust gas to the engine without the use of manifold vacuum. The valve controls exhaust gas flow from the exhaust system to the intake manifold through three orifices, to produce seven combinations. When the solenoid is energized, the armature, combined with an attached shaft and swivel pintle, is raised and the orifice is opened.
The flow accuracy is dependent on the orifice size only, which results in improved EGR control.




TEST DESCRIPTION: The numbers below refer to circled numbers on the diagnostic chart.

1. Codes should be diagnosed before doing a functional check.
2. This step activates each solenoid individually. As you energize #1 or #2 solenoids, the engine rpm should drop. The engine may stall when the #3 solenoid is energized as it has a large port.

NOTE: Once the test sequence is completed, clear codes and verify NO "SERVICE ENGINE SOON" light exists.

NOTE:

In the preceeding test the scan tool is grounding each EGR solenoid individually through a quad driver circuit in the ECM. Grounding the solenoids will open the passage and cause a drop in engine RPM.



INCORRECT EGR OPERATION:

1. If too much EGR is flowing at idle, cruise, or cold operation,
any of the following conditions could exists:
a. The engine dies after cold start.
b. The engine stalls on deceleration.
c. The vehicle surges during cruise mode.
d. Rough idle.

2. If too little or no exhaust gases flow, the combustion chamber temperature may increase under acceleration or heavy load conditions. These conditions could cause:
a. Detonation (Spark Knock).
b. The engine to overheat.
c. The emissions test to fail.