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Diagnosis & Repair (Using OBD-II Scan Tool)

  1. Disconnect EGR temperature sensor harness connector. EGR temperature sensor is located on manifold, between EGR valve and intake air chamber (built into EGR valve). Measure resistance between EGR temperature sensor terminals (component side). If resistance is 2.5-600 k/ohms, go to next step. If resistance is not 2.5-600 k/ohms, replace EGR temperature sensor.
  2. Check for open or short in wiring between EGR temperature sensor and ECM. See WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
  3. Check plugged, cracked and disconnected EGR system vacuum hoses. See VACUUM DIAGRAMS article. If problem exists, repair vacuum hoses as necessary. If problem does not exist, go to next step.
  4. Access ECM behind glove box. See Figure. Turn ignition off. Disconnect ECM harness connector E9. See Figure. Using a jumper wire, backprobe between terminal No. 20 (Yellow/Green wire) at ECM harness connector E9 and terminal No. 28 (Brown wire) at ECM harness connector E10. Apply air pressure to EGR Vacuum Switching Valve (VSV) port "E". EGR VSV is located under "V" bank cover on top of engine. With jumper wire connected, air should flow from port "F". See Figure. With jumper wire disconnected, air should flow from port "G". If EGR VSV operates as specified, go to step  8. If EGR VSV does not operate as specified, go to next step.
  5. Disconnect EGR VSV harness connector. Measure resistance between EGR VSV terminals (component side). Resistance should be 27-33 ohms at 68°F (20°C). Measure resistance between each terminal and body of EGR VSV (component side). Resistance should be infinite. If resistance is not as specified, replace EGR VSV. If resistance is as specified, go to next step.
  6. Check for open in EGR VSV circuits between engine compartment fuse block and ECM. See WIRING DIAGRAMS article. Repair as necessary. If circuits are okay, repair or replace power source circuit.
  7. Check EGR system. See EXHAUST GAS RECIRCULATION SYSTEM in SYSTEM & COMPONENT TESTING article. Repair EGR system as necessary. If EGR system is okay, go to next step.
  8. Disconnect vacuum hose from EGR valve. Start engine and let idle. Apply vacuum to EGR valve. If engine does not run rough or stall, replace EGR valve or clean EGR passage. If engine runs rough or stalls, go to next step.
    9. NOTE: EGR position sensor is an integral part of EGR valve.
  9. Check EGR position sensor and EGR VCV. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - V6 & V8 article. If problem exists, repair as necessary. If problem does not exist, replace ECM.
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