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Home >> Lexus >> 2000 >> SC 400 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic 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. Turn scan tool on. Using scan tool, monitor ECT sensor temperature. If temperature displayed is same as actual coolant temperature, 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 connector. Connect a fused jumper wire between ECT sensor harness connector terminals. Turn ignition on. Using scan tool, monitor ECT sensor temperature.
  3. If temperature displayed is 284°F (140°C) or more, check ECT sensor connector for corrosion, damage or loose terminals. If sensor connector is okay, replace ECT sensor and retest. If temperature displayed is not 284°F (140°C) or more, turn ignition off. Remove fused jumper wire. Backprobing, connect fuse jumper wire between terminals No. 14 (Light Green wire) and No. 18 (Brown wire) at ECM E16 connector. See Figure.
  4. If temperature displayed on scan tool is 284°F (140°C) or more, check for an open in Light Green wire and Brown wire between ECT sensor connector and ECM E16 connector. 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 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 and go to next step.
  6. Disconnect E16 connector from ECM. Turn ignition on. If temperature displayed is -40°F (-40°C), check for short in Light Green wire and Brown wire between ECT sensor and ECM E16 connector. If temperature displayed by scan tool is not -40°F (-40°C), replace ECM and retest.
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