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Home >> Lexus >> 1997 >> LS 400 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Circuit Tests >> DTC P0115: Engine Coolant Temperature (ECT) Sensor Circuit >> Diagnosis & Repair

Diagnosis & Repair

  1. Connect scan tool to Data Link Connector (DLC) No. 3. See Figure. Turn ignition on. Using scan tool, monitor ECT sensor temperatu re. If temperature displayed is same as engine coolant temperature, check 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 ECT 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. Using scan tool, monitor ECT sensor temperature.
  3. If temperature displayed is 284°F (140°C) or more, replace ECT sensor and retest. If temperature displayed is less than 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 tool is 284°F (140°C) or more, check and repair wiring harness between ECT harness connector and ECM. If temperature displayed on scan tool 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 tool 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), repair short circuit in wiring harness between ECT sensor and ECM. If temperature displayed by scan tool is not -40°F (-40°C), replace ECM and retest.
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