626 1999-2001

Engine Coolant Temperature Sensor

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Operation



Specific to:

Mazda 626 1999-2002

The coolant temperature sensor is a variable resistor that is influenced by temperature. Which means, as the temperature changes, so does the resistance inside the sensor. The computer reads this change in resistance to determine the operating temperature of the engine. It uses this reading to determine proper air/fuel mixture and ignition timing settings.

Removal & Installation



Specific to:

Mazda 626 1999-2002

  1. Partially drain the engine cooling system until the coolant level is below the ECT sensor-mounting hole.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Detach the wiring harness connector from the ECT sensor.
  6.  
  7. Using an open-end wrench, remove the coolant temperature sensor from the intake manifold or thermostat housing.
  8.  

To install:

  1. Thread the sensor into the intake manifold, or thermostat housing, by hand, then tighten it securely.
  2.  
  3. Connect the negative battery cable.
  4.  
  5. Refill the engine cooling system.
  6.  
  7. Start the engine, check for coolant leaks and top off the cooling system.
  8.  

Testing



Specific to:

Mazda 626 1999-2002

  1. Remove the ECT.
  2.  
  3. Place the sensor in water with a thermometer and heat the water gradually.
  4.  
  5. Measure the resistance of the sensor and compare to the following values:

    68°F (20°C)-35.5-39.2 kohms
     
    140°F (60°C)-7.18-7.92 kohms
     

  6.  
  7. If not as specified, replace the ECT.
  8.  
  9. If within specification, check wiring harness and connectors between ECT and PCM.
  10.  

 
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