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Diagnosis & Repair (Using Lexus Scan Tool)

  1. Connect Lexus scan tool to Data Link Connector (DLC) No. 3. See Figure. Turn ignition on. Using scan tool, read EGR gas temperature. Temperature should be 302°F (150°C) or less (not immediately after driving). If temperature is as specified, go to step 4). If temperature is not as specified, go to next step.
    NOTE: If EGR gas temperature displayed is 318.7°F (159.3°C), a short exists in EGR gas temperature sensor circuit.
  2. Disconnect EGR gas temperature sensor. Sensor is mounted on EGR valve. EGR gas temperature displayed should be 37.6°F (3.1°C). If temperature displayed is not as specified, go to next step. If temperature displayed is as specified, check sensor connectors and terminals. Repair as necessary. If connectors are okay, replace sensor and retest.
  3. Turn ignition off. Access ECM behind glove box. Disconnect ECM "B" connector. See Figure. Turn ignition on and observe scan tool display. EGR gas temperature displayed should be 37.6°F (3.1°C). If temperature displayed is not as specified, replace ECM and retest. If temperature displayed is as specified, repair wiring harness between ECM "B" connector and EGR gas temperature sensor connector.
  4. Connect Check Harness "A" (SST 09990-01000) to ECM. See TEST PREPARATION under SELF-DIAGNOSTIC SYSTEM 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.
  5. Locate 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.
  6. 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.
  7. 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.
  8. If VSV meets all specifications in steps 6) and 7), check circuits between EGR VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
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