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Diagnosis & Repair

WARNING: This page is about a different car, the 2002 Toyota Sequoia. However, it is still accessible from the selected car via links, so may be relevant.
  1. Connect Toyota hand-held tester or scan tool to Data Link Connector (DLC) No. 3 at driver's side of instrument panel. See Figure. Turn ignition on and then turn hand-held tester or scan tool on.
  2. Using hand-held tester or scan tool, read engine coolant temperature for ECT sensor. If displayed engine coolant temperature is -40°F (-40°C), go to next step. If displayed engine coolant temperature is 284°F (140°C) or more, go to step  8. If displayed engine coolant temperature is same as actual engine coolant temperature, problem is intermittent. Check for defective connections or intermittent problem in wiring between ECT sensor and ECM. ECT sensor is located on passenger's side of coolant pipe at front of engine, in front of intake manifold and contains Black 2-pin electrical connector with Green/White and Green/Yellow wires. ECM is located behind glove box and heater duct. See Figure.
  3. Turn ignition off. Disconnect electrical connector at ECT sensor. ECT sensor is located on passenger's side of coolant pipe at front of engine, in front of intake manifold and contains Black 2-pin electrical connector with Green/White and Green/Yellow wires. Connect jumper wire between both terminals on electrical connector for ECT sensor.
  4. Turn ignition on. Using hand-held tester or scan tool, read engine coolant temperature for ECT sensor. If displayed engine coolant temperature is less than 284°F (140°C), go to next step. If displayed engine coolant temperature is 284°F (140°C) or more, check for defective electrical connections at ECT sensor and electrical connector. If electrical connections are defective, repair as necessary. If electrical connections are okay, replace ECT sensor. See ENGINE COOLANT TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.
  5. Turn ignition off. Remove jumper wire. Remove glove box and heater duct (if necessary) for access to ECM with electrical connectors still installed on ECM. See Figure. Ensure electrical connectors at ECM are securely installed so all terminals in electrical connectors are contacting terminals in ECM.
  6. Ensure electrical connector at ECT sensor is still disconnected. Connect jumper wire between terminals No. 14 (Green/Yellow wire) and No. 18 (Green/White wire) at ECM electrical connector E7 with all electrical connectors installed on ECM. See Figure. This is the THW and E2 terminals on ECM.
  7. Turn ignition on. Using hand-held tester or scan tool, read engine coolant temperature for ECT sensor. If displayed engine coolant temperature is 284°F (140°C) or more, repair open Green/Yellow wire or Green/White wire between ECT sensor and ECM. See WIRING DIAGRAMS article. If displayed engine coolant temperature is not 284°F (140°C) or more, replace ECM.
  8. Turn ignition off. Disconnect electrical connector at ECT sensor. ECT sensor is located on passenger's side of coolant pipe at front of engine, in front of intake manifold and contains Black 2-pin electrical connector with Green/White and Green/Yellow wires.
  9. Turn ignition on. Using hand-held tester or scan tool, read engine coolant temperature for ECT sensor. If displayed engine coolant temperature is not -40°F (-40°C), go to next step. If displayed engine coolant temperature is -40°F (-40°C), replace ECT sensor. See ENGINE COOLANT TEMPERATURE SENSOR under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.
  10. Turn ignition off. Remove glove box and heater duct (if necessary) for access to ECM with electrical connectors still installed on ECM. See Figure. Disconnect ECM electrical connector E7. See Figure. Ensure electrical connector is still disconnected at ECT sensor.
  11. Turn ignition on. Using hand-held tester or scan tool, read engine coolant temperature for ECT sensor. If displayed engine coolant temperature is -40°F (-40°C), repair short in wiring harness and electrical connectors between ECT sensor and ECM. See WIRING DIAGRAMS article. If displayed engine coolant temperature is not -40°F (-40°C), replace ECM.
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