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Home >> Toyota >> 2004 >> Matrix Base, FWD, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 18 (Engine Control System Self-Diagnostics) >> Diagnostic Tests >> DTC P0115: Engine Coolant Temperature Sensor Circuit >> Diagnosis & Repair
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Diagnosis & Repair

WARNING: This page is about a different car, the 2002 Toyota Prius. 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 flywheel end of cylinder head and contains a Dark Gray 2-pin electrical connector with White and Brown wires. ECM is located behind glove box. See Figure.
  3. Turn ignition off. Disconnect electrical connector at ECT sensor. ECT sensor is located on flywheel end of cylinder head and contains a Dark Gray 2-pin electrical connector with White and Brown 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. Manufacturer states that converter and inverter assembly must be removed for servicing of ECT sensor. The converter and inverter assembly are involved with the high-voltage system used on this vehicle and service procedure should only be performed by authorized dealer.
  5. Turn ignition off. Remove jumper wire. Remove glove box 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 (White wire) and No. 18 (Brown wire) at ECM electrical connector E8 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 Brown wire or 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 flywheel end of cylinder head and contains a Dark Gray 2-pin electrical connector with White and Brown 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. Manufacturer states that converter and inverter assembly must be removed for servicing of ECT sensor. The converter and inverter assembly are involved with the high-voltage system used on this vehicle and service procedure should only be performed by authorized dealer.
  10. Turn ignition off. Remove glove box for access to ECM with electrical connectors still installed on ECM. See Figure. Disconnect ECM electrical connector E8. 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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