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Diagnosis & Repair (Using OBD-II Scan Tool)

  1. Disconnect EGR gas temperature sensor. Sensor is mounted on EGR valve. 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. Check for short circuit in wiring harness between EGR gas temperature sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring harness 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 section. Turn ignition on. Connect a jumper wire between ground and terminal No. 75 (Gray wire) at ECM "B" connector.
  4. Located EGR Vacuum Switching Valve (VSV). See appropriate illustration in VACUUM DIAGRAMS article. With jumper wire connected, VSV is on. Apply air pressure to VSV port "E". Air should flow from port "F". See Figure. Disconnect jumper wire. No air should flow from port "F". If VSV operates correctly, check EGR valve. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM/COMPONENT TESTS article. If VSV 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. Apply air pressure to VSV port "E". 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 VSV meets all specifications in steps 5) and 6), check circuits between EGR VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring harness is okay, replace ECM and retest.
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