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Test NTC-18A: Checking EGR System

NOTE: This test applies to vehicles equipped with diesel engine only. For component location, see appropriate THEORY & OPERATION article.
  1. Turn ignition off. Inspect condition and routing of all EGR hoses. See VACUUM DIAGRAMS article. Repair or replace hoses as necessary and perform TEST VER-2A: ROAD TEST VERIFICATION . If hoses are okay, go to next step.
  2. Start engine and allow it to idle. Using scan tool, select EGR SYSTEM TEST. Select No. 2. Monitor Intake Air Temperature (IAT) until it stabilizes. Go to next step.
  3. Using scan tool, actuate EGR solenoid and allow EGR to flow. Monitor IAT. If IAT does not rise after EGR solenoid is actuated, go to step 5)  . If IAT rises, go to next step.
  4. Inspect all related wiring and connectors. Repair wiring and connectors as necessary and perform TEST VER-2A: ROAD TEST VERIFICATION . If wiring and connectors are okay, go to next step.
  5. Disconnect vacuum supply hose at EGR solenoid. If vacuum is not present at EGR solenoid, repair vacuum supply to EGR as necessary and perform TEST VER-2A: ROAD TEST VERIFICATION . If vacuum is present, go to next step.
  6. Reconnect vacuum supply hose to EGR solenoid. Disconnect EGR valve-to-EGR solenoid vacuum hose at EGR solenoid. If EGR solenoid does not allow vacuum to flow, replace EGR solenoid and perform TEST VER-2A: ROAD TEST VERIFICATION . If EGR solenoid allows vacuum to flow, go to next step.
  7. Reconnect vacuum hose to EGR solenoid. Disconnect EGR valve-to-EGR solenoid vacuum hose at EGR valve. If vacuum is not flowing through hose, repair vacuum or check valve as needed and perform TEST VER-2A: ROAD TEST VERIFICATION . If vacuum is flowing, go to next step.
  8. Turn ignition off. Stop EGR system test. Remove EGR valve. Connect hand vacuum pump to EGR valve. Slowly apply 10 in. Hg to EGR valve while watching EGR valve poppet. If EGR valve poppet does not start to open at 10 in. Hg, replace EGR valve assembly and perform TEST VER-2A: ROAD TEST VERIFICATION . If poppet begins to open at 10 in. Hg, ensure no carbon build-up exists in EGR tube or in intake and exhaust manifolds and retest EGR system.
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