Toyota Pick-ups, Land Cruiser, and 4 Runner 1997-00

Engine Coolant Temperature (ECT) Sensor

Print

OPERATION



The Engine Coolant Temperature (ECT) sensor is a thermistor (a resistor that changes resistance value, based on temperature) mounted in the engine coolant stream. As the temperature of the engine coolant changes, the resistance of the coolant sensor changes. Low coolant temperature produces a high resistance: 100,000 ohms at 40° F (40° C). High temperature causes low resistance: 70 ohms at 284° F (140° C).

The ECM supplies a 5-volt signal to the coolant sensor and measures the voltage that returns. By measuring the voltage change, the ECM determines the engine coolant temperature. The voltage will be high when the engine is cold and low when the engine is hot. This information is used to control fuel management, IAC, spark timing, EGR, canister purge and other engine operating conditions.

TESTING



  1. Remove the ECT sensor from the engine.
  2.  
  3. Fill a clean container with water and measure its temperature.
  4.  
  5. Place the sensor tip into the water. Measure the resistance of the ECT sensor with an ohmmeter. Compare the resistance with the temperature as per the graph.
  6.  



Click image to see an enlarged view

Fig. Submerge the end of the temperature sensor in cold or hot water and check resistance



Click image to see an enlarged view

Fig. Temperature sensor resistance graph

  1. If it is not within specifications, replace the sensor.
  2.  
  3. Install the ECT sensor.
  4.  

REMOVAL & INSTALLATION



1FZ-FE, 2RZ-FE and 3RZ-FE Engines
  1. Drain the engine cooling system.
  2.  
  3. Disconnect the engine wire protector from the brackets if used.
  4.  
  5. Detach the ECT sensor wiring.
  6.  
  7. Using a deep socket, remove the ECT sensor and gasket.
  8.  

To install:

  1. Using a new gasket and deep socket, install the ECT sensor. Tighten to 14 ft. lbs. (20 Nm).
  2.  
  3. Connect the ECT wiring to the sensor.
  4.  
  5. Install the engine wire protector to the brackets if used.
  6.  
  7. Fill the cooling system, start the engine, and top off the system.
  8.  

5VZ-FE Engine
  1. Drain the engine cooling system.
  2.  
  3. Disconnect the upper radiator hose from the water outlet.
  4.  
  5. Disconnect the power steering air hose from the clamp.
  6.  
  7. Disconnect the three cord clamps of the spark plug wires from the belt cover.
  8.  
  9. Remove the mounting bolts for the timing belt cover and gasket.
  10.  
  11. Disconnect the camshaft position sensor harness.
  12.  
  13. Remove the fuel pipe.
  14.  
  15. Disconnect the ECT sensor harness.
  16.  
  17. Using a 19mm deep socket, remove the sensor and gasket.
  18.  

To install:

  1. Using a new gasket and deep socket, install the ECT sensor. Tighten to 14 ft. lbs. (20 Nm).
  2.  
  3. Connect the ECT wiring to the sensor.
  4.  
  5. Reinstall the fuel pipe with four new gaskets; tighten to 25 ft. lbs. (34 Nm).
  6.  
  7. Attach the timing belt cover, tighten to 80 inch lbs. (9 Nm).
  8.  
  9. Reconnect the upper radiator hose to the water outlet.
  10.  
  11. Fill the cooling system, start the engine, and top off. Check for leaks.
  12.  

2UZ-FE Engine
  1. Drain the engine coolant.
  2.  
  3. Remove the cosmetic/acoustic throttle body cover
  4.  
  5. Remove the air intake connector elbow from the throttle body. There are several vacuum hoses, which should be tagged for identification before removal, if required.
  6.  
  7. Remove the throttle body from the intake manifolds using the following as a guide:
    1. Disconnect the accelerator cable from the throttle body.
    2.  
    3. Remove the two bolts and two nuts and separate the throttle body from the intake.
    4.  
    5. Discard the gasket. A new gasket will be required at assembly.
    6.  

  8.  
  9. Detach the electrical connector from the ECT. Remove the ECT sensor. Remove and discard the O-ring seal. A new seal will be required at assembly.
  10.  



Click image to see an enlarged view

Fig. Exploded view of the ECT sensor and the components you need to remove for access to the sensor2UZ-FE engine

To install:

  1. Using a new seal, install the ECT sensor. Tighten to 15 ft. lbs. (20 Nm). Attach the electrical connector.
  2.  
  3. Using a new gasket, install the throttle body to the intake manifold. Tighten the nuts and bolts to 13 ft. lbs. (18 Nm). Connect the throttle cable.
  4.  
  5. Install the intake air connector and attach the vacuum lines that were removed.
  6.  
  7. Refill the cooling system with approved coolant.
  8.  
  9. Install the start the engine and check for leaks.
  10.  
  11. Install the cosmetic/acoustic throttle body cover.
  12.  

 
label.common.footer.alt.autozoneLogo