Component Diagnosis Charts - C3 System

Chart C-7:

EGR Circuit:

CIRCUIT DESCRIPTION:
The digital Exhaust Gas Recirculation (EGR) valve is designed to accurately supply EGR to an engine independent of intake 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 a solenoid is energized, the armature with attached shaft and swivel pintle is lifted opening the orifice.

The flow accuracy is dependent on metering orifice size only, which results in improved control.

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

1. DTC(s) 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 Exhaust Gas Recirculation (EGR) valve shows signs of excessive heat, a melted condition, check the exhaust system for blockage (possibly a plugged converter). If the exhaust system is restricted, repair the cause, one of which might be an injector which is open due to one of the following:

a. Stuck EGR valve pintles.
b. Grounded driver circuit.
c. Possibly defective ECM.
d. EGR valve is wired in correctly. If this condition is found, the oil should be checked for possible fuel contamination.