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Diagnosis & Repair (Using OBD-II Scan Tool)

  1. Check all EGR system vacuum hoses. See VACUUM DIAGRAMS article. If problem exists, replace vacuum hoses as necessary. If problem does not exist, go to next step.
  2. Disconnect EGR VSV vacuum hoses. Access ECM behind bottom center of instrument panel, in front of console. Disconnect ECM harness connector E4 and connect a jumper wire between ground and terminal No. 23 (Black/White wire) at ECM harness connector E4. See Figure. Turn ignition on. Apply air pressure to EGR VSV port "E". See Figure. With jumper wire connected, EGR VSV should be on and air should flow from small filter on end of EGR VSV. Disconnect jumper wire. Air should flow from port "G". If EGR VSV operates as specified, go to step  5. If EGR VSV does not operate as specified, go to next step.
  3. Turn ignition off. Disconnect EGR VSV harness connector. Measure resistance between EGR VSV terminals (component side). Resistance should be 33-39 ohms at 68°F (20°C). Check continuity between each terminal and body of EGR VSV. Continuity should not exist. If readings are as specified, go to next step. If readings are not as specified, replace EGR VSV.
  4. Apply battery voltage and ground to EGR VSV terminals. Air applied to port "E" should flow from small filter on end of EGR VSV. Remove battery voltage from valve terminals. Air applied to port "E" should flow from port "G". If EGR VSV does not operate as specified, replace EGR VSV. If EGR VSV operates as specified, repair open or short in wiring between engine compartment fuse block and ECM. See WIRING DIAGRAMS article.
  5. Perform exhaust gas recirculation system test. See EXHAUST GAS RECIRCULATION (EGR) SYSTEM TEST under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, repair as necessary. If problem does not exist, go to next step.
  6. Check EGR vacuum modulator. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, replace EGR vacuum modulator. If problem does not exist, go to next step.
  7. Check EGR valve. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, replace EGR valve. If problem does not exist, go to next step.
  8. Check Manifold Absolute Pressure (MAP) sensor. See ENGINE SENSORS & SWITCHES in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, replace MAP sensor. If problem does not exist, replace ECM.
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