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Home >> Lexus >> 1997 >> 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 OBD-II Scan Tool)

Diagnosis & Repair (Using OBD-II Scan Tool)

  1. Remove EGR temperature sensor. Place sensor and a thermometer into a container of water. Heat container and check sensor resistance. If resistance is as specified, go to next step. See the EGR TEMPERATURE SENSOR RESISTANCE SPECIFICATIONSs table below. If resistance is not as specified, replace sensor.
    EGR TEMPERATURE SENSOR RESISTANCE SPECIFICATIONS

    Temperature °F (°C) Ohms
    122 (50) 64,000-97,000
    212 (100) 11,000-16,000
    302 (150) 2000-4000
  2. Check for open or short circuit in wiring harness between EGR temperature sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If wiring is okay, go to next step.
  3. Check EGR valve. See SYSTEM/COMPONENT TESTS article. Replace EGR valve as necessary. If EGR valve is okay, replace ECM and retest.
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