LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Lexus >> 1996 >> 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 Tester)
April 5, 2026: LEMON Manuals is launched! Read the announcement.

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 "B" 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 "B" connector and EGR gas temperature sensor connector.
  4. Check EGR valve. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING article. Replace EGR valve as necessary. If EGR valve is okay, replace ECM and retest.
scientia non olet · About LEMON Manuals