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Home >> Lexus >> 1996 >> ES 300 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Circuit Tests >> DTC P0402 - Excessive EGR Flow Detected >> Diagnosis & Repair (Using Lexus Scan Tester)
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Diagnosis & Repair (Using Lexus Scan Tester)

  1. Remove instrument panel fuse cover. Connect Lexus scan tester to Data Link Connector (DLC) No. 3. See Figure. Turn ignition and scan tester on. 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. If temperature displayed is 318.7°F (159.3°C), a short circuit exists in EGR temperature sensor circuit. Repair as necessary.
  2. Disconnect EGR temperature sensor. Connector is located underneath throttle body. 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, inspect 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 E9 connector. See Figure. Turn ignition on and observe scan tester 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 E9 connector and EGR temperature sensor connector.
  4. On scan tester, select ACTIVE TEST mode. Check operation of VSV when activated by scan tester. VSV is located under intake plenum cover. Start and run engine. With EGR system off, air should exhaust from small filter on end of valve. With EGR system on, air should pass through valve and exit vacuum fitting at bottom of valve. If valve does not operate correctly, go to next step. If valve operates correctly, inspect EGR valve. See SYSTEM/COMPONENT TESTS article. Replace as necessary.
  5. Remove EGR VSV. Using ohmmeter, measure resistance between valve terminals. Resistance should be 26-46 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 exhaust from small filter on end of valve. Remove jumper wires from VSV terminals. Air should pass through valve. 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.
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