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Home >> Lexus >> 1995 >> LS 400 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - OBD-II >> Diagnostic Testing >> Code P0402: Excessive EGR Flow Detected >> Diagnosis & Repair (Using Lexus Scan Tester)
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Diagnosis & Repair (Using Lexus Scan Tester)

  1. 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 gas temperature sensor circuit. Repair as necessary.
  2. Disconnect EGR gas temperature sensor. 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 E12 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 E12 connector and EGR gas temperature sensor connector.
  4. Check EGR valve. See SYSTEM & COMPONENT TESTING. Replace EGR valve as necessary. If EGR valve is okay, replace ECM and retest.
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