Mitsubishi Galant/Mirage/Diamante 1990-2000

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 the coolant temperature increases, and increases as the coolant temperature decreases. This provides a reference signal to the PCM, which indicates engine coolant temperature. The signal sent to the PCM by the ECT sensor helps the PCM to determine spark advance, EGR flow rate, air/fuel ratio, and engine temperature. The ECT is a two wire sensor, a 5-volt reference signal is sent to the sensor and the signal return is based upon the change in the measured resistance due to temperature.

TESTING





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Fig. Unplug the ECT sensor electrical connector



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Fig. Test the resistance of the ECT sensor across the two sensor pins



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Fig. Another method of testing the ECT is to submerge it in cold or hot water and check resistance



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Fig. The ECT can be monitored with an appropriate and Data-stream capable scan tool

  1. Drain the engine coolant to a level below the intake manifold.
  2.  
  3. Disconnect the sensor wiring harness and remove the coolant temperature sensor from the engine.
  4.  
  5. Place the temperature sensing portion of the sensor into a pan of hot water. Use a thermometer to monitor the water temperature.
  6.  
  7. Measure the resistance across the sensor terminals while the sensor is in the water. Compare obtained reading to specifications:
  8.  

  1. Water temperature of 32°F (0°C)-5.1-6.5 kilo-ohms present
  2.  
  3. Water temperature of 68°F (20°C)-2.1-2.7 kilo-ohms present
  4.  
  5. Water temperature of 104°F (40°C)-0.9-1.3 kilo-ohms present
  6.  
  7. Water temperature of 176°F (80°C)-0.26-0.36 kilo-ohms present
  8.  

  1. If the resistance differs greatly from standard value, replace the sensor.
  2.  

REMOVAL & INSTALLATION





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Fig. Unplug the ECT sensor electrical connector



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Fig. Use a deep socket and an extension to reach the ECT sensor . . .



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Fig. . . . then remove the ECT sensor from the thermostat housing



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Fig. Before installation, coat the threads of the sensor with a suitable sealant

  1. Disconnect the negative battery cable.
  2.  
  3. Drain the engine coolant to a level below the intake manifold.
  4.  
  5. Unplug the sensor wiring harness.
  6.  
  7. Unthread and remove the sensor from the engine.
  8.  

To install:

  1. Coat the threads of the sensor with a suitable sealant and thread into the housing.
  2.  
  3. Tighten the sensor to 22 ft. lbs. (30 Nm).
  4.  
  5. Refill the cooling system to the proper level.
  6.  
  7. Attach the electrical connector to the sensor securely.
  8.  
  9. Connect the negative battery cable.
  10.  

 
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