Nissan Maxima 1993-1998 Repair Guide

Engine Coolant Temperature Sensor

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OPERATION



The Engine Coolant Temperature (ECT) sensor resistance changes in response to engine coolant temperature. The sensor resistance decreases as coolant temperature increases. This provides a reference signal, which indicates engine coolant temperature, to the ECM.

TESTING



See Figures 1 and 2



Click image to see an enlarged view

Fig. Fig. 1: Use an ohmmeter to measure the resistance between the two terminals

  1. Disconnect the engine electrical harness from the ECT sensor.
  2.  
  3. Connect an ohmmeter between the ECT sensor terminals.
  4.  
  5. With the engine cold and the ignition switch in the OFF position, measure and note the ECT sensor resistance.
  6.  
  7. Connect the engine electrical harness to the sensor.
  8.  
  9. Start the engine and allow it to reach normal operating temperature.
  10.  
  11. Once the engine has reached normal operating temperature, turn it OFF .
  12.  
  13. Once again, disconnect the engine electrical harness from the ECT sensor.
  14.  
  15. Measure and note the ECT sensor resistance with the engine hot.
  16.  
  17. Compare the cold and hot ECT sensor resistance measurements with the accompanying chart.
  18.  
  19. If readings do not approximate those in the chart, the sensor may be faulty.
  20.  



Click image to see an enlarged view

Fig. Fig. 2: Compare the sensor readings with these values

REMOVAL & INSTALLATION



See Figure 3



Click image to see an enlarged view

Fig. Fig. 3: Location of the thermal sending unit (A) next to the coolant temperature sensor (B)

  1. Partially drain the engine cooling system until the coolant level is below the ECT sensor mounting hole.
  2.  
  3. Disconnect the electrical harness from the ECT sensor.
  4.  
  5. Remove the coolant temperature sensor from the cylinder head.
  6.  

To install:
  1. Coat the sensor threads with Teflon® sealant.
  2.  
  3. Thread the sensor into the intake manifold and tighten securely.
  4.  
  5. Refill the engine cooling system.
  6.  
  7. Start the engine and check for coolant leaks.
  8.  
  9. Top off the cooling system as necessary.
  10.  

 
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