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Home >> Lexus >> 1996 >> LS 400 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Circuit Tests >> DTC P0401 - Insufficient Exhaust Gas RECIRCULATION (EGR) Flow Detected >> Diagnosis & Repair (Using Lexus Scan Tester)

Diagnosis & Repair (Using Lexus Scan Tester)

  1. Connect Lexus scan tester to DLC No. 3. Turn ignition on. 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. If temperature displayed is 37.6°F (3.1°C), locate and repair open circuit in EGR temperature sensor circuit.
  2. Disconnect EGR temperature sensor harness connector. 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, inspect 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 jumper wire between ECM harness connector terminals No. 2 (Red/Yellow wire) at ECM E12 connector and No. 22 (Brown wire) at ECM E13 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 in circuits between ECM and EGR temperature sensor. If temperature displayed is not as specified, replace ECM and retest.
  5. Check EGR valve. See SYSTEM & COMPONENT TESTING article. Replace EGR valve as necessary. If EGR valve is okay, replace ECM and retest.
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