Exhaust Gas Recirculation: Testing and Inspection

Chart C-7:

Wiring Diagram EGR Circuit:

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 EGR flow from the exhaust to the intake manifold through three orifices, which increment in size 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 using appropriate chart before preparing a functional check.

2. This step activates each solenoid individually. As you energize #1 or #2 solenoid, the engine rpm should drop. #3 solenoid has the large port and may stall the engine when energized.


NOTE:

If the digital EGR valve shows signs of excessive heat distortion, check the exhaust system for blockage (possibly a plugged converter) using the procedure in EMISSION CONTROLS/DIAGNOSING AND TESTING PROCEDURES/TESTING PROCEDURES/CATALYTIC CONVERTER. If the exhaust system is restricted, repair the cause, one of which may be a stuck open injector caused by a grounded driver circuit, defective ECM, or a stuck injector. If this condition is found, be sure and check the engine oil for fuel contamination.