For a complete wiring diagram Refer to Section 8WWhen Monitored:With the engine running.Set Condition:The ECM detects EGR flow is less than the requested flow.Possible CausesAIR FILTERAIR RESTRICTIONCHECKING FOR AIR LEAKSCHECKING THE EGR AIR FLOW CONTROL VALVECHECKING THE EGR COOLER AND TUBESEGR VALVEINTERMITTENT CONDITION1. CHECK FOR ACTIVE DTCIf the ECM detects and stores a DTC, the ECM also stores the engine/vehicle operating conditions under which the DTC was set. Some of these conditions are displayed on the scan tool at the same time the DTC is displayed.Before erasing stored DTCs, record these conditions. Attempting to duplicate these conditions may assist when checking for an active DTC.Turn the ignition on.With the scan tool, erase ECM DTCs.Test drive the vehicle and monitor the scan tool for ECM DTCs.If there are any Mass Air Flow DTC's, diagnose the MAF DTC's before continuing EGR diagnostics.Did this DTC set again?YesGo To 2NoRefer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure.(Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)2. AIR FILTERTurn the ignition off.Remove and inspect the Air Filter for soiling or excessive dirt and debris which may cause air flow restriction.Were any of these problems found?YesReplace the Air Filter element.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 33. AIR RESTRICTIONInspect all air intake, crankcase vent and turbocharger related tubes for damage, restriction or poor connection. Any of these conditions can cause this DTC to set.Inspect the exhaust system and related tubes for damage, restriction or poor connection. Any of these conditions can cause this DTC to set.Inspect the intake system, exhaust system and related tubes and connections.Were any problems found?YesRepair or replace as necessary.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 44. CHECKING FOR AIR LEAKSRemove the Inlet Pressure Sensor.Connect smoke machine 84-04 to the Inlet Pressure Sensor port in the intake duct and begin injecting smoke into the intake system.Observe all intake system components for evidence of smoke leakage.Is there evidence of smoke leakage?YesRepair or replace as necessary.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 55. CHECKING EGR AIR FLOW CONTROL VALVE (EGR AFCV)Disconnect the air tube at the inlet port of the EGR Air Flow Control Valve.Turn the ignition on.Use a mirror to observe the motion of the EGR Air Flow Control Valve in the following step.The EGR AFCV should be normally open (allowing full air flow) then close during actuation.With the scan tool, actuate the “Throttle Valve” while observing the EGR Air Flow Control Valve.Does the EGR AFCV close completely when actuated?YesGo To 6NoReplace the EGR Air Flow Control Valve.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)6. CHECKING EGR COOLER AND TUBESTurn the ignition off.Gain access to and inspect the EGR Cooler and both tubes that connect to the EGR Cooler. Check tubes and cooler for damage, leaks, excessive carbon build up and other problems that could restrict or prevent proper exhaust gas flow. Compressed air ( at low pressure ) can be applied to the lower port of the EGR Cooler. When applying compressed air check for air to flow through cooler and out the upper port. Always wear safety glasses when working with compressed air.Were any problems found?YesRepair or replace as necessary.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 77. CHECKING THE EGR VACUUM SUPPLYRefer to the symptom Checking The EGR Vacuum Supply to check for proper EGR vacuum supply and EGR Solenoid operation.Were any problems found?YesRepair or replace as necessary.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoReplace the EGR Valve.Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)