Exhaust Gas Recirculation: Testing and Inspection

EGR Diagnostic Chart (Chart C-7):

EGR Solenoid Valve Circuit Diagram:

TEST DESCRIPTION (numbers below refer to circled numbers on diagnostic chart)

NOTE: Always check for trouble codes before attempting diagnosis of the EGR system. If there are codes present, correct these first.

1. You should be able to discern a change in engine speed as each solenoid is cycled "ON" and "OFF" again. The #3 solenoid may cause the engine to stall when cycled "ON" with the engine idling.

2. If test light lites, PCM and wiring are OK.

3. If the digital EGR valve shows signs of excessive heat, check the exhaust system for restriction (restricted catalytic converter). If the exhaust is restricted, repair this first and check for the cause. Possible causes are:
Misfiring ignition system or fouled spark plugs.
Stuck or leaking injector.
Grounded injector driver circuit or defective PCM (injectors energized all the time.)
Excessive oil burning due to bad pistons, rings, or valve guides.

NOTE: EGR solenoids can be cycled "ON" and "OFF" manually by using the following supplemental procedure.

1. Instead of using a "SCAN" tool, start engine and disconnect EGR solenoid harness connector.
2. With engine idling, connect fused battery power (12 volts) to terminal "D" of solenoid valve assembly.
3. Ground terminal "C" of solenoid valve assembly (energizes solenoid #3).
^ Engine should stumble &/or die. If not check EGR passages for restriction. If passages are OK, replace EGR valve.
4. Ground terminal "B" of solenoid valve assembly (energizes solenoid #2).
^ You should notice a change in engine speed. If not, check EGR passages for restriction. If passages are OK, replace EGR valve.
5. Ground terminal "A" of solenoid valve assembly (energizes solenoid #1).
^ You should notice a change in engine speed and the engine may stumble and die. If not, check EGR passages for restriction. If passages are OK, replace EGR valve.

When testing is complete, clear trouble codes (you should have generated codes 53, 54, &/or 55 if you performed test without a "SCAN" tool). Operate vehicle, then re-check to make sure there are no recuring codes.