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Home >> Lexus >> 1997 >> SC 400 >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Circuit Tests >> DTC P0401 - Insufficient Exhaust Gas RECIRCULATION (EGR) Flow Detected >> Diagnosis & Repair (Using Lexus Scan Tool)

Diagnosis & Repair (Using Lexus Scan Tool)

  1. Connect Lexus scan tool. Turn ignition on. Using scan tool, read EGR gas temperature. Temperature should be 50°F (10°C). If temperature is as specified, go to step 5). If temperature is not as specified, go to next step.
    NOTE: If EGR gas temperature displayed is 37.6°F (3.1°C), an open exists in EGR gas temperature sensor circuit.
  2. Disconnect EGR gas temperature sensor harness connector. Connector is located near throttle body. Connect jumper wire between harness connector terminals. EGR gas temperature displayed should be 318.7°F (159.3°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. Remove jumper wire. Turn ignition off. Access ECM behind glove box. Connect Check Harness "A" (SST 09990-01000) to ECM. See TEST PREPARATION under SELF-DIAGNOSTIC SYSTEM. Connect jumper wire between ECM harness connector terminals No. 46 (Black/Red wire) and No. 65 (Brown wire) at ECM "B" connector. See Figure. Turn ignition on. EGR gas temperature displayed should be 318.7°F (159.3°C).
  4. If temperature displayed is as specified, locate and repair open circuit in wiring harness between ECM and EGR gas temperature sensor. If temperature displayed is not as specified, replace ECM and retest.
  5. 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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