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Home >> Lexus >> 1995 >> LS 400 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - OBD-II >> Diagnostic Testing >> Code P0115: Engine Coolant Temperature (ECT) Sensor Circuit >> Diagnosis & Repair Procedure
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Diagnosis & Repair Procedure

  1. Connect scan tester to Data Link Connector (DLC) No. 3. See Figure. Turn ignition on. Turn scan tester on. Monitor ECT sensor temperature. If temperature displayed is same as engine coolant temperature, inspect component and ECM connections. Problem is intermittent.
  2. If temperature displayed is 284°F (140°C), go to step 5). If temperature displayed is -40°F (-40°C), turn ignition off. Disconnect MAF sensor harness connector. Connect a jumper wire between terminals No. 2 (Red/Blue wire) and No. 1 (Brown wire) at ECT sensor harness connector. Turn ignition on. Monitor ECT sensor temperature on scan tester.
  3. If temperature displayed is 284°F (140°C) or more, replace ECT sensor and retest. If temperature displayed is not 284°F (140°C), turn ignition off. Remove jumper wire. Access ECM behind glove box. Connect jumper wire between terminals No. 20 (Red/Blue wire) and No. 22 (Brown wire) at ECM E13 connector. See Figure.
  4. If temperature displayed on scan tester is 284°F (140°C) or more, inspect and repair circuits between ECT harness connector and ECM. If temperature displayed on scan tester is not 284°F (140°C) or more, replace ECM and retest.
  5. Turn ignition off. Disconnect ECT sensor harness connector. Turn ignition on. If temperature displayed on scan tester is -40°F (-40°C), replace ECT sensor and retest. If temperature displayed is not -40°F (-40°C), turn ignition off.
  6. Access ECM behind glove box. Disconnect ECM E13 connector. Turn ignition on. If temperature displayed is -40°F (-40°C), inspect and repair circuits between ECT sensor and ECM for short. If temperature displayed by scan tester is not -40°F (-40°C), replace ECM and retest.
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