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Diagnosis & Repair

  1. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC) No. 3. See Figure. Turn ignition on. Using hand-held tester or scan tool, monitor Engine Coolant Temperature (ECT) sensor temperature. If temperature displayed is same as actual coolant temperature, problem is intermittent. Check component and ECM connections. If temperature displayed is -40°F (-40°C), go to next step. If temperature displayed is 284°F (140°C) or more, go to step  4.
  2. Turn ignition off. Disconnect ECT sensor harness connector (2-pin harness connector with Green/Black wire and Brown/White wire). Using a jumper wire, connect ECT sensor harness connector terminals. Turn ignition on. Using hand-held tester or scan tool, monitor ECT sensor temperature. If temperature displayed is less than 284°F (140°C), go to next step. If temperature displayed is 284°F (140°C) or more, replace ECT sensor.
  3. Turn ignition off. Remove jumper wire. Access ECM behind glove box. See Figure. Using a jumper wire, backprobe between terminals No. 18 (Brown/White wire) and No. 14 (Green/Black wire) at ECM harness connector E6. See Figure. If temperature displayed is 284°F (140°C) or more, repair open in Green/Black wire and/or Brown/White wire between ECT sensor and ECM. See WIRING DIAGRAMS article. If temperature displayed is less than 284°F (140°C), replace ECM.
  4. Turn ignition off. Disconnect ECT sensor harness connector. Turn ignition on. If temperature displayed is not -40°F (-40°C), go to next step. If temperature displayed is -40°F (-40°C), replace ECT sensor.
  5. Turn ignition off. Access ECM behind glove box. See Figure. Disconnect ECM harness connector E6. See Figure. Turn ignition on. If temperature displayed is -40°F (-40°C), repair short in Green/Black wire between ECT sensor and ECM. See WIRING DIAGRAMS article. If temperature displayed is not -40°F (-40°C), replace ECM.
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