GM Cavalier/Sunbird/Skyhawk/Firenza 1982-1994

Engine Coolant Temperature (ECT) Sensor

Print

OPERATION



See Figure 1

The Engine Coolant Temperature (ECT) sensor, sometimes referred to as the Coolant Temperature Sensor (CTS), is a thermistor (resistor which changes value based on temperature) mounted in the engine coolant stream. Low coolant temperatures produce a high resistance - 100,000 ohms at -40°F (-40°C), while high temperatures cause low resistance - 70 ohms at 266°F (130°C).



Click image to see an enlarged view

Fig. Fig. 1: Engine Coolant Temperature (ECT) sensor and connector

The control module provides a 5 volt reference signal to the sensor through a resistor in the module and measures the voltage. The voltage will be high when the engine is cold and low when the engine is hot. By measuring the voltage, the control module knows the engine coolant temperature. The engine coolant temperature affects most other systems controlled by the module.

TESTING



See Figure 2



Click image to see an enlarged view

Fig. Fig. 2: ECT sensor value chart

  1. Disconnect the temperature sensor.
  2.  
  3. Connect an ohmmeter between the sensor terminals.
  4.  
  5. Measure the resistance with the engine off and cool. Then measure with the engine running and warmed up. Compare the resistance values obtained with the chart.
  6.  
  7. Replace the sensor if the readings are incorrect.
  8.  

REMOVAL & INSTALLATION



See Figure 3

  1. Disconnect the negative battery cable.
  2.  
  3. Properly relieve the cooling system pressure, then drain to a level below the sensor.
  4.  
  5. Detach the ECT sensor electrical connector.
  6.  
  7. Carefully remove the sensor.
  8.  

To install:


Click image to see an enlarged view

Fig. Fig. 3: Location of the ECT sensor - 2.2L engine shown

  1. Coat the threads of the sensor with a suitable sealant. Install the sensor into the engine, tighten to 19 ft. lbs. (25 Nm).
  2.  
  3. Attach the ECT sensor electrical connector.
  4.  
  5. Refill the cooling system to the proper level.
  6.  
  7. Connect the negative battery cable.
  8.  

 
label.common.footer.alt.autozoneLogo