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OPERATION

A power voltage that 5 V is applied to the engine coolanttemperature sensor calculation terminal (terminal No. 1) native the engine-ECU (terminal No. 26).The power voltage is earthed to the engine-ECU (terminal No. 27) native the enginecoolant temperature sensor (terminal No. 2).

You are watching: P0118 engine coolant temperature circuit high input

FUNCTION

The engine coolant temperature sensor converts the enginecoolant temperature right into a voltage signal, and inputs the voltage to the engine-ECU.In response to the signal, the engine-ECU controls the fuel injection amount andthe fast idle speed once the engine is cold state.The engine coolant temperature sensor is a kind of resistor, which has characteristicsto alleviate its resistance as the engine coolant temperature rises. Therefore, the sensor outputvoltage varies with the engine coolant temperature, and becomes reduced as the engine coolant temperaturerises.

TROUBLE JUDGMENT

Check Condition
Ignition switch is "ON" position.Judgement CriterionEngine coolant temperature sensor output voltage is an ext than 4.6 V (correspondingto one engine coolant temperature the -40°C or less) because that 2 seconds.FAIL-SAFE and BACKUP FUNCTIONControl as if the engine coolant temperature is 80°C.

PROBABLE CAUSES

Failed engine coolant temperature sensorOpen circuit or harness damage in engine coolant temperature sensor circuit or loosened connectorcontactFailed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III data list

Item 6: Engine coolant temperature sensor
OK:Engine cold state: at ambient temperature (atmospheric temperature) or equivalent.Engine warm state: at 80 -120°C

Q. Is the check result normal?

Intermittent breakdown (Refer to group 00 -How to usage Troubleshooting/InspectionService point out -How to Cope with Intermittent Malfunctions ).
Go to step 2.

STEP 2. Connector check: B-10 engine coolant temperature sensor connector

Q. Is the check an outcome normal?

Go to action 3.
Repair or change the connector.

STEP 3. Perform resistance measurement in ~ B-10 engine coolant temperaturesensor connector.

Disconnect connector, and measure in ~ sensor side.Resistance between terminal No. 1 and also No. 2.
OK:Engine coolant temperature at -20°C: 14 -17 kΩEngine coolant temperature in ~ 0°C: 5.1 -6.5 kΩEngine coolant temperature in ~ 20°C: 2.1 -2.7 kΩEngine coolant temperature in ~ 40°C: 0.9 -1.3 kΩEngine coolant temperature at 60°C: 0.48 -0.68 kΩEngine coolant temperature in ~ 80°C: 0.26 -0.36 kΩ

Q. Is the check result normal?

Go to action 4.
Replace the engine coolant temperature sensor.

STEP 4. Perform voltage measurement in ~ B-10 engine coolant temperaturesensor connector.

Disconnect connector, and also measure at harness side.Ignition switch: ONVoltage in between terminal No. 1 and also earth.
OK: 4.5 -4.9 V

Q. Is the check an outcome normal?

Go to step 8.
Go to action 5.

STEP 5. Connector check: B-08 engine-ECU connector

Q. Is the check result normal?

Go to step 6.
Repair or change the connector.

STEP 6. Examine harness between B-10 (terminal No. 1) engine coolanttemperature sensor connector and also B-08 (terminal No. 26) engine-ECU connector.

Check output line for open up circuit.

Q. Is the check result normal?

Go to action 7.
Repair the damaged harness wire.

STEP 7. M.U.T.-III data list

Item 6: Engine coolant temperature sensor
OK:Engine cold state: at ambient temperature (atmospheric temperature) or equivalent.Engine hot state: at 80 -120 °C

Q. Is the check an outcome normal?

Intermittent malfunction (Refer to team 00 -How to usage Troubleshooting/InspectionService clues -How come Cope v Intermittent Malfunctions ).
Replace the engine-ECU.

STEP 8. Do resistance measurement at B-10 engine coolant temperaturesensor connector.

Disconnect connector, and measure at harness side.Resistance in between terminal No. 2 and earth.
OK: continuous (2 Ωor less)

Q. Is the check result normal?

Go to step 11.
Go to step 9.

STEP 9. Connector check: B-08 engine-ECU connector

Q. Is the check result normal?

Go to step 10.
Repair or change the connector.

STEP 10. Examine harness in between B-10 (terminal No. 2) engine coolanttemperature sensor connector and B-08 (terminal No. 27) engine-ECU connector

Check earthing heat for open up circuit and also damage.

Q. Is the check result normal?

Go to step 7.
Repair the damaged exploit wire.

STEP 11. Connector check: B-08 engine-ECU connector

Q. Is the check result normal?

Go to step 12.
Repair or replace the connector.

STEP 12. Inspect harness between B-10 (terminal No. 1) engine coolanttemperature sensor connector and also B-08 (terminal No. 26) engine-ECU connector.

Check calculation line because that damage.

Q. Is the check result normal?

Go to action 7.

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Repair the damaged exploit wire.
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