LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Lexus >> 1996 >> SC 300 Automatic >> 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 gas temperature sensor circuit. Repair as necessary.
  2. Disconnect EGR gas 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. Connect Check Harness "A" (SST 09990-01000) to ECM connectors, leaving ECM disconnected. See TEST PREPARATION under SELF-DIAGNOSTIC SYSTEM. Turn ignition on. Connect a jumper wire between ground and terminal No. 75 (Gray wire) at ECM "B" connector.
  5. Vacuum Switching Valve (VSV) is located under intake plenum. With jumper wire connected, VSV is on. Air should flow from port "F". See Figure. Disconnect jumper wire. No air should flow from port "F". If valve operates correctly, check EGR valve. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING article. If valve 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. 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 valve meets all specifications in steps 6) and 7), inspect circuits between EGR VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
scientia non olet · About LEMON Manuals