Acura Coupes and Sedans 1994-2000 Repair Information

Engine Coolant Temperature Sensor

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OPERATION



See Figure 1

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Fig. Fig. 1: Resistance vs. engine temperature for a typical coolant temperature sensor

The Engine Coolant Temperature (ECT) sensor is a thermistor, a sensor whose 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 also is used for temperature gauge operation by sending it's signal to the instrument cluster. The ECT sensor 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



See Figures 2, 3, 4 and 5

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Fig. Fig. 2: Unplug the ECT sensor to access the sensor



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Fig. Fig. 3: Another method of testing the ECT is to submerge it in cold or hot water and check resistance



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Fig. Fig. 4: The ECT can be monitored with an appropriate and Data-stream capable scan tool



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Fig. Fig. 5: ECT and IAT resistance-to-temperature specifications

  1. Disconnect the engine wiring 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 wiring harness to the sensor.
  8.  
  9. Start the engine and allow the engine to reach normal operating temperature.
  10.  
  11. Once the engine has reached normal operating temperature, turn the engine OFF .
  12.  
  13. Once again, disconnect the engine wiring 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.  

REMOVAL & INSTALLATION



  1. Disconnect the negative battery cable.
  2.  
  3. Drain and recycle the engine coolant to a level below the sensor.
  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. Detach the ECT sensor connector.
  2.  
  3. Remove the ECT sensor from the thermostat housing
  4.  

To install:
  1. Coat the sensor threads with Teflon® sealant.
  2.  
  3. Thread the sensor into position and tighten.
  4.  
  5. Attach the ECT sensor connector.
  6.  
  7. Connect the negative battery cable.
  8.  
  9. Refill the engine cooling system.
  10.  
  11. Start the engine and check for coolant leaks.
  12.  
  13. Bleed the cooling system.
  14.  

 
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