Engine Coolant Temperature Sensor

* Begin work only after the engine has completely cooled down.

Inspection

PROCEDURE
1. If the sensor fails, first check the fuses (see Subsection 12.1).
2. If, shortly after starting the engine, the sensor indicates an excessively high temperature, refer to Subsection 1.9.
3. If the gauge shows "Hot" immediately after starting a cold engine, disconnect the sensor wire. On 4E-FE engines the sensor is screwed into the side of the thermostat housing, and on 4A-FE and 7A-FE engines into the coolant pump pipe. If the reading drops, replace the sensor. If the reading remains high, the cause may be a short to ground in the sensor wire or a faulty sensor.
4. If the sensor stops indicating temperature after the engine has fully warmed up (approximately 10 minutes after starting), and the fuses are good, proceed as follows. Stop the engine, disconnect the sensor wire, and use a jumper wire to connect the sensor wire to a clean, bare metal part of the engine. Turn the ignition on briefly, but do not start the engine. If the sensor now shows "Hot", replace the sensor.
5. If there is no sensor reading, the cause may be an open circuit or a faulty sensor.

Replacement

PROCEDURE
1. Drain the coolant (see Subsection 2.8.4).
2. Disconnect the sensor wiring connector.
3. Using a deep socket or open-end wrench, remove the sensor.
4. Install the new sensor and tighten securely. Do not apply sealant to the sensor threads, as this may interrupt the sensor body ground contact.
5. Connect the wiring connector, refill with coolant, start the engine, and check for leaks and proper engine operation.