ParkAvenue 1997-1999

Engine Coolant Temperature Sensor

Print

Operation



Specific to:

Buick LeSabre 1986-1999

Buick Park Avenue 1996-1999

Oldsmobile 88 1992-1999

Oldsmobile Delta 88 1986-1988

Oldsmobile LSS 1996-1999

Pontiac Bonneville 1987-1999

The coolant temperature sender changes resistance as the coolant temperature increases and decreases.

Specific to:

Buick LeSabre 1986-1999

Buick Park Avenue 1996-1999

Oldsmobile 88 1992-1999

Oldsmobile Delta 88 1986-1988

Oldsmobile LSS 1996-1999

Pontiac Bonneville 1987-1999

Most engine functions are affected by the coolant temperature. Determining whether the engine is hot or cold is largely dependent on the temperature of the coolant. An accurate temperature signal to the PCM is supplied by the coolant temperature sensor or Engine Coolant Temperature (ECT) sensor. The coolant temperature sensor is a thermistor mounted in the engine coolant stream. A thermistor is an electrical device that varies its resistance in relation to changes in temperature. Low coolant temperature produces a high resistance, and high coolant temperature produces low resistance. The PCM supplies a signal of 5 volts to the coolant temperature sensor through a resistor in the PCM and measures the voltage. The voltage will be high when the engine is cold and low when the engine is hot.



Click image to see an enlarged view

Fig. Engine Coolant Temperature (ECT) sensor and connector

Removal & Installation



Specific to:

Buick LeSabre 1986-1999

Buick Park Avenue 1996-1999

Oldsmobile 88 1992-1999

Oldsmobile Delta 88 1986-1988

Oldsmobile LSS 1996-1999

Pontiac Bonneville 1987-1999

  1. Disconnect the negative battery cable.
  2.  
  3. Drain the coolant to a level below the coolant temperature sender.
  4.  
  5. Unplug the sender electrical connector, then unscrew the sender. The sender can usually be found mounted in the engine block or threaded into the thermostat housing/outlet or radiator.
  6.  

To install:

  1. Install the sender in the vehicle and tighten securely.
  2.  
  3. Attach the sender electrical connector.
  4.  
  5. Refill the cooling system to the proper level with the proper type and amount of coolant.
  6.  
  7. Connect the negative battery cable.
  8.  

Specific to:

Buick LeSabre 1986-1999

Buick Park Avenue 1996-1999

Oldsmobile 88 1992-1999

Oldsmobile Delta 88 1986-1988

Oldsmobile LSS 1996-1999

Pontiac Bonneville 1987-1999

  1. Disconnect the negative battery cable.
  2.  
  3. Drain the radiator into a suitable container, to a level below the sensor.
  4.  
  5. For 1986-91 vehicles, perform the following:
    1. Properly relieve the fuel system pressure, as outlined in Section 5.
    2.  
    3. Unfasten the 10mm bolt and bracket holding the fuel line to the throttle cable bracket.
    4.  
    5. Loosen the fuel supply and return lines from the fuel rail and carefully move aside.
    6.  
    7. Fabricate a loop of wire or use a long prytool to slip under the locking tab of the electrical connector and gently pull on the tab to disengage it.
    8.  

  6.  
  7. For 1992-99 vehicles, perform the following:
    1. Remove the air induction tube or rear air intake duct, as applicable.
    2.  
    3. Detach the sensor electrical connector.
    4.  

  8.  
  9. Using a 19mm deep well socket and extension, remove the sensor.
  10.  



Click image to see an enlarged view

Fig. Location of the ECT sensor - 3.8L (VIN L) engine shown



Click image to see an enlarged view

Fig. Exploded view of the ECT sensor mounting - 3.8L (VIN 1) engine



Click image to see an enlarged view

Fig. ECT sensor location - 3.8L (VIN 1) engine



Click image to see an enlarged view

Fig. Insert the ECT sensor into its mounting hole - 1996-99 vehicles

To install:

  1. Coat the ECT sensor threads with a suitable sealant.
  2.  
  3. Install the sensor and tighten to 22 ft. lbs. (30 Nm).
  4.  
  5. For 1992-99 vehicles perform the following:
    1. Attach the sensor electrical connector.
    2.  
    3. For VIN 1 and L engines, install the air induction tube.
    4.  

  6.  
  7. For 1986-91 vehicles, perform the following:
    1. Attach the electrical connector.
    2.  
    3. Connect the fuel supply and return lines.
    4.  
    5. Install the fuel line bracket.
    6.  

  8.  
  9. Connect the negative battery cable, then refill the cooling system.
  10.  

Testing



Specific to:

Buick LeSabre 1986-1999

Buick Park Avenue 1996-1999

Oldsmobile 88 1992-1999

Oldsmobile Delta 88 1986-1988

Oldsmobile LSS 1996-1999

Pontiac Bonneville 1987-1999

  1. Remove the temperature sender from the engine.
  2.  
  3. Position the water temperature sending unit in such a way that the metal shaft (opposite end from the electrical connectors) is situated in a pot of water. Make sure that the electrical connector is not submerged and that only the tip of the sending unit's body is in the water.
  4.  
  5. Heat the pot of water at a medium rate. While the water is warming, continue to measure the resistance of the terminal and the metal body of the sending unit:
    1. As the water warms up, the resistance exhibited by the ohmmeter goes down in a steady manner: the sending unit is good.
    2.  
    3. As the water warms up, the resistance does not change or changes in erratic jumps: the sender is bad, replace it with a new one.
    4.  

  6.  
  7. Install the good or new sending unit into the engine, then connect the negative battery cable.
  8.  

Sensor Installed In Vehicle

Specific to:

Buick LeSabre 1986-1999

Buick Park Avenue 1996-1999

Oldsmobile 88 1992-1999

Oldsmobile Delta 88 1986-1988

Oldsmobile LSS 1996-1999

Pontiac Bonneville 1987-1999

  1. Unfasten the retaining bolts, then remove the bracket.
  2.  



Click image to see an enlarged view

Fig. Unfasten the retainers, then remove the throttle bracket for more access to the sensor

  1. Use a long screwdriver or prytool to lift the ECT sensor locking tab and detach the connector.
  2.  



Click image to see an enlarged view

Fig. Use a long screwdriver to carefully lift the sensor locking tab, then unplug the connector

  1. Attach an ohmmeter to the sensor terminals, then measure the resistance and compare with the accompanying chart.
  2.  



Click image to see an enlarged view

Fig. Use needlenose pliers to attach an ohmmeter to the sensor terminals, then measure resistance (tested at 80°F)



Click image to see an enlarged view

Fig. Engine Coolant Temperature (ECT) and Intake Air Temperature (IAT) sensor temperature vs. resistance values



Click image to see an enlarged view

Fig. Engine Coolant Temperature (ECT) and Throttle Position (TP) sensor circuits

Sensor Removed From Vehicle

Specific to:

Buick LeSabre 1986-1999

Buick Park Avenue 1996-1999

Oldsmobile 88 1992-1999

Oldsmobile Delta 88 1986-1988

Oldsmobile LSS 1996-1999

Pontiac Bonneville 1987-1999

  1. Remove the ECT sensor from the vehicle.
  2.  
  3. Immerse the tip of the sensor in a container of water.
  4.  



Click image to see an enlarged view

Fig. Submerge the end of the temperature sensor in cold or hot water and check resistance

  1. Connect a digital ohmmeter to the two terminal of the sensor.
  2.  
  3. Using a calibrated thermometer, compare the resistance of the sensor to the temperature of the water. Refer to the accompanying resistance value chart.
  4.  
  5. Repeat the test at two other temperature points, heating or cooling the water as necessary.
  6.  
  7. If the sensor does not meet specifications, it must be replaced.
  8.  

 
label.common.footer.alt.autozoneLogo