Mitsubishi Eclipse 1990-1998 Repair Guide

Engine Coolant Temperature (ECT) Sensor

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OPERATION



The engine coolant temperature sensor is located on the thermostat housing. It is a resistor type sensor which detects the engine coolant temperature. The warm-up state of the engine is judged from the sensor output voltage. When a cold signal is sent to the ECU, the fuel injection amount, idle revolution speed and the injection timing are suitably controlled.

When the coolant temperature sensor is faulty, the engine coolant temperature is regarded as being 176°F (80°C). Because of this, engine starting may be difficult, driveability may become poor and the idle quality may suffer during cold operating conditions. The trouble may not be noticed when the engine is at normal operating temperature.

TESTING



Except 1995-98 2.0L Non-Turbo Engine

See Figure 1

  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.  



Click image to see an enlarged view

Fig. Fig. 1: Measure resistance with the ECT sensor in a pan of water-except 1995-98 2.0L turbo engines

  1. Place the temperature sensing portion of the sensor into a pan of hot water. Use a thermometer to monitor the water temperature.
  2.  
  3. Measure the resistance across the sensor terminals while the sensor is in the water. Compare obtained reading to specifications:
    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.  

  4.  
  5. If the resistance differs greatly from standard value, replace the sensor.
  6.  

1995-98 2.0L Non-Turbo Engine

See Figure 2

  1. Detach the engine coolant temperature sensor connector.
  2.  
  3. Measure the resistance between the sensor terminals, and compare with the following specifications:
    1. At 77°F (25°C) the resistance should be 9-11 kilo-ohms.
    2.  

  4.  



Click image to see an enlarged view

Fig. Fig. 2: Measure the resistance of the engine coolant temperature sensor (1) with an ohmmeter (2)-1996 2.0L engine shown

    1. At 212°F (100°C) the resistance should be 0.6-0.8 kilo ohms.
    2.  


  1. If resistance falls outside of specifications, replace the sensor.
  2.  

REMOVAL & INSTALLATION



See Figures 3, 4, 5 and 6

  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.  



Click image to see an enlarged view

Fig. Fig. 3: Unplug the ECT sensor electrical connector

  1. Unthread and remove the sensor from the engine.
  2.  



Click image to see an enlarged view

Fig. Fig. 4: Use a deep socket and an extension to reach the ECT sensor ...



Click image to see an enlarged view

Fig. Fig. 5: ... then remove the ECT sensor from the thermostat housing

To install:
  1. Coat the threads of the sensor with a suitable sealant and thread into the housing.
  2.  



Click image to see an enlarged view

Fig. Fig. 6: Before installation, coat the threads of the sensor with a suitable sealant

  1. Tighten the sensor to 22 ft. lbs. (30 Nm) for all except 1995-98 2.0L non-turbo engines. For 1995-98 2.0L non-turbo engines, tighten the sensor to 5 ft. lbs. (7 Nm).
  2.  
  3. Refill the cooling system to the proper level.
  4.  
  5. Attach the electrical connector to the sensor securely.
  6.  
  7. Connect the negative battery cable.
  8.  

 
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