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Home >> Lexus >> 1996 >> SC 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. Remove instrument panel fuse cover. Connect Lexus scan tester. 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), there is an open EGR gas temperature sensor circuit. Repair as necessary.
  2. Disconnect EGR gas temperature sensor harness connector. Connector is located underneath 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, 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 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 (Brown/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 in circuits 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 TESTING article. Replace EGR valve as necessary. If EGR valve is okay, replace ECM and retest.
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