Diagnosis & Repair
WARNING: This page is about a different car, the 2002 Lexus ES 300. However, it is still accessible from the selected car via links, so may be relevant.
- 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, check component and ECM connections. Problem is intermittent. If temperature displayed is 284°F (140°C), go to step 4. If temperature displayed is -40°F (-40°C), go to next step.
- Turn ignition off. Disconnect ECT sensor harness connector. Connect a fused jumper wire between terminals No. 2 (Green/Black wire) and No. 1 (Brown wire) at ECT sensor harness connector. Turn ignition on. Using scan tool, monitor ECT sensor temperature. If temperature displayed is 284°F (140°C) or more, ensure ECT connector is okay. If connector is okay, replace ECT sensor and retest system. If temperature displayed is less than 284°F (140°C), go to next step.
- Turn ignition off. Remove fused jumper wire. Access ECM behind glove box. Backprobing, connect a fused jumper wire between ECM connector E10 terminals No. 19 (Green/Black wire) and No. 28 (Brown wire). See Figure. If temperature displayed on scan tool is 284°F (140°C) or more, repair open in Brown or Green/Black wire between ECT sensor harness connector and ECM E10 connector. If temperature displayed on scan tool is not 284°F (140°C) or more, replace ECM and retest system.
- 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 system. If temperature displayed is not -40°F (-40°C), turn ignition off and go to next step.
- Access ECM behind glove box. Disconnect ECM E10 connector. Turn ignition on. If temperature displayed is -40°F (-40°C), locate and repair short circuit in wiring harness between ECT sensor and ECM E10 connector. See Figure. If temperature displayed by scan tool is not -40°F (-40°C), replace ECM and retest system.