Exhaust Gas Recirculation (EGR) System Check

Chart C-7:

EGR Wiring Diagram:

EGR SYSTEM CHECK

CIRCUIT DESCRIPTION:

The EGR valve is controlled by a normally closed solenoid (vacuum flows when energized). The ECM powers the solenoid, and monitors the vacuum to the EGR.
A code 32 will detect a faulty solenoid, vacuum supply, EGR Valve, or plugged passage. This chart checks for plugged EGR passages, a sticking EGR valve, or a stuck open or inoperative solenoid.




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

1. With the ignition on and engine not running, the solenoid should not be energized and vacuum should not flow to the EGR valve.
2. Grounding the diagnostic terminal will power the solenoid and vacuum should flow to the valve.
3. This checks for plugged EGR passages. If the passages are plugged, severe engine detonation may result.
4. The EGR solenoid will not be energized in Neutral or Park. This test is used to check the Park/Neutral switch input to the ECM.

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





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.