Exhaust Gas Recirculation: Testing and Inspection

Exhaust Gas Recirculation (EGR) Flow Check:

Exhaust Gas Recirculation (EGR) Circuit:

Circuit Description:
The linear 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 an orifice with a PCM controlled pintle.

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

1. Ensures that the EGR valve is allowing EGR flow and the PCM is capable of controlling the EGR valve. The engine should run extremely rough and may even stall at the 75% and 100% positions.
2. Ensures that CKT 435 is not shorted to ground.
3. Ensures that CKT 435 is not open and that the PCM driver is functioning properly.

Diagnostic Aids:
An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation.

Check for:

^ Poor connection or damaged harness. Inspect PCM harness connectors for backed out terminal "RA16", improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
^ Intermittent test. If connections and harness check OK, monitor a digital voltmeter connected between "RA16" and ground while moving related connectors and wiring harness. If the failure is induced, the voltage reading will change.
^ Check for a restriction in EGR tube or passage. Also, ensure there is not excessive carbon buildup on EGR valve pintle and orifice.

If the linear EGR valve shows signs of excessive heat, check the exhaust system for blockage (possibly a plugged converter). If the exhaust system is restricted, repair the cause; possibly an ignition misfire or an injector which is open due to one of the following:

^ Stuck
^ Grounded driver circuit
^ Possibly defective PCM

If this condition is found, the oil should be checked for possible fuel contamination.