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Home >> Lexus >> 1997 >> SC 400 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Circuit Tests >> DTC P0402 - Excessive EGR Flow Detected >> Diagnosis & Repair (Using Lexus Scan Tool)
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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 temperature sensor circuit.
  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, 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. 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. Check EGR valve. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM/COMPONENT TESTS article. Replace EGR valve as necessary. If EGR valve is okay, replace ECM and retest.
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