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Diagnosis & Repair (Using OBD-II Scan Tester)

  1. Disconnect EGR gas temperature sensor. Connector is located underneath throttle body. Using ohmmeter, measure resistance between sensor terminals. If resistance is 2500 ohms or more (not immediately after driving), go to next step. If resistance is less than 2500 ohms, replace sensor and retest.
  2. Inspect circuits between EGR gas temperature sensor and ECM for short circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, go to next step.
  3. Connect Check Harness "A" (SST 09990-01000) to ECM connectors, leaving ECM disconnected. See TEST PREPARATION under SELF-DIAGNOSTIC SYSTEM. Turn ignition on. Connect a jumper wire between ground and terminal No. 75 (Gray wire) at ECM "B" connector.
  4. Vacuum Switching Valve (VSV) is located under intake plenum. With jumper wire connected, VSV is on. Air should flow from port "F". See Figure. Disconnect jumper wire. No air should flow from port "F". If valve operates correctly, check EGR valve. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING article. If valve does not operate correctly, go to next step.
  5. Remove EGR VSV. Using ohmmeter, measure resistance between valve terminals. Resistance should be 39-45 ohms. Measure resistance between each terminal and body of valve. Resistance should be infinite. If resistance is as specified, go to next step. If resistance is not as specified, replace VSV.
  6. Using jumper wires, apply battery voltage to VSV terminals. Air should flow from port "F". Remove jumper wires from VSV terminals. No air should pass through port "F". Replace VSV as necessary.
  7. If valve meets all specifications in steps 5) and 6), inspect circuits between EGR VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, replace ECM and retest.
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