Chrysler Full-Size Vans 1989-1998 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 the coolant temperature increases, and increases as the coolant temperature decreases. This provides a reference signal to the ECM, which indicates engine coolant temperature. The signal sent to the ECM by the ECT sensor helps the ECM to determine spark advance, EGR flow rate, air/fuel ratio, and engine temperature.

TESTING



See Figures 1, 2 and 3

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the engine cover.
  4.  

Be sure you are unplugging and checking the ECT, and not the temperature gauge sending unit; they are two different parts.

  1. Unplug the connector on the sensor.
  2.  
  3. Test the resistance of the sensor across the two terminals of the sensor.
  4.  
  5. With the engine cold, and ambient temperature below 90°F (32°C), the resistance should be between 500-1100 ohms.
  6.  
  7. With the engine at normal operating temperature, the resistance should be greater than 1300 ohms.
  8.  
  9. If the sensor is not within specifications, replace it.
  10.  



Click image to see an enlarged view

Fig. Fig. 1: The coolant temperature sensor can be tested using the Auto Xray or equivalent tool's data display feature



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Fig. Fig. 2: The ECT sensor's electrical connector terminal identification



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Fig. Fig. 3: ECT sensor circuit diagram

REMOVAL & INSTALLATION



See Figures 4 and 5

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the engine cover.
  4.  


CAUTION
Never open, service or drain the radiator or cooling system when hot; serious burns can occur from the steam and hot coolant. Also, when draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantities. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

  1. Drain and recycle the engine coolant.
  2.  
  3. Remove the air cleaner assembly.
  4.  
  5. On vehicles with air conditioning:
    1. Remove the A/C compressor to intake manifold bracket.
    2.  
    3. Fabricate a 8 inch long hook tool from a coat hanger to remove the wiring harness connector.
    4.  

  6.  
  7. Remove the connector from the sensor.
  8.  
  9. Remove the sensor from the intake manifold.
  10.  

To install:
  1. Install the sensor in the manifold and tighten to 8 ft. lbs. (11 Nm).
  2.  
  3. Install the connector on the sensor.
  4.  
  5. On vehicles with air conditioning:
    1. Install the A/C bracket.
    2.  

  6.  
  7. Replace the air cleaner assembly.
  8.  
  9. Refill and bleed the engine cooling system.
  10.  
  11. Connect the negative battery cable.
  12.  
  13. Inspect for leaks.
  14.  
  15. Install the engine cover.
  16.  



Click image to see an enlarged view

Fig. Fig. 4: The engine coolant temperature sensor is located at the base of the intake manifold, between the A/C compressor and alternator (generator)



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Fig. Fig. 5: Location of the ECT sensor with neighboring components removed

 
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