DTC 39: EGR Function
With engine at normal operating temperature and transmission in Neutral, lift EGR valve diaphragm. Engine should run rough and RPM should decrease. If engine does not run rough, check EGR transfer pipe, intake manifold, and EGR valve for blockage.
If engine runs rough, apply parking brake and service brakes. With engine hot, ensure vacuum signal to EGR valve is present at 1200 RPM. If vacuum signal is not present, ensure ECM is grounding EGR control solenoid Green/Red wire or check vacuum hose routing.
If vacuum signal is present, ensure EGR valve functions properly when vacuum is applied. Replace EGR valve if necessary. Ensure ECM is receiving EGR temperature sensor signal. See the appropriate SENSOR RANGE CHARTS article in this section. Check continuity of wiring harness between ECM and EGR temperature sensor. Repair or replace as necessary.

Answered by Dave H (expert)
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