Toyota 89422-20010 Sensor, Water Temperature

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If the coolant temperature gauge isn't working, check the fuses. If the gauge reads hot on a cold start, disconnect the wire at the coolant temperature sending unit. If the gauge drops, replace the unit. If the gauge doesn't show up after warming up, detach the wire at the unit, connect it to clean ground, and switch on the ignition.

To troubleshoot issues with the coolant temperature gauge, start by checking the fuses if the gauge is inoperative. If the temperature indicator shows excessive temperature after running for a while, it may indicate a problem. In the case where the gauge indicates "Hot" shortly after starting the engine cold, disconnect the wire at the Coolant Temperature Sensor. If the gauge reading drops, replace the sending unit. If the reading remains high, there may be a shorted wire to the gauge or a faulty gauge. If the coolant temperature gauge fails to indicate after the engine has warmed up and the fuses are fine, shut off the engine. If the gauge still doesn't work, there may be an open circuit or a faulty gauge. For replacement, start by releasing any pressure in the radiator by removing and reinstalling the cap when the engine is cool. Disconnect the electrical connector from the sending unit and apply sealant to the threads of the new sending unit. Unscrew the old sending unit and quickly install the new one to prevent coolant loss. Tighten the sending unit securely and connect the wiring harness. Refill the cooling system, run the engine, and check for leaks and proper gauge operation.

To start with, the Coolant Temperature Sensor uses a thermistor that adjusts its resistance based on temperature changes. This resistance variation directly affects the voltage signal sent from the sensor to the PCM. Problems with the ECT sensor circuits will trigger a diagnostic trouble code. To check the ECT sensor, detach the electrical connector and measure the resistance between the sensor's terminals using an ohmmeter. The resistance should be between 2,500 and 3,000 ohms at room temperature. When the sensor is warmed in water, the resistance should decrease to around 250 to 300 ohms at 180 degrees F. If the test results are incorrect, you will need to replace the ECT sensor. Then replace the sensor, drain about one gallon of coolant, wrap the threads of the new sensor with Teflon sealing tape, disconnect the electrical connector, and detach the old sensor. After that, the installation is the reverse step of the removal process. Finally, you can refill the cooling system.

Shut off the engine and connect the wire at the sending unit to a clean ground on the engine. If the gauge now indicates hot, replace the sending unit. If the gauge still does not work, there may be an open circuit or a faulty gauge.

It should be done by a dealer service department due to the need for special tools and test equipment.

The new unit should be installed and tightened securely. Thread sealant should not be used as it may electrically insulate the sending unit.

If the resistance values are correct, check the circuit for the proper reference voltage by turning the ignition key ON (engine not running) and measuring the voltage at the coolant temperature sensor connector. It should be approximately 5 volts.

On 1979 through 1981 models, it is in the front part of the intake manifold; on 1982 through 1986 models, it is on the thermostat housing; and on 1987 and later models, it is next to the cold start injector time switch.

The fuses should be checked if the gauge is inoperative.

This part goes into a water jacket on the engine block

This sensor reads the temperature of the coolant