GM Lumina/Grand Prix/Cutlass Supreme/Regal 1988-1996

Coolant Temperature Sensor (CTS)

Print

OPERATION



See Figure 1

Click image to see an enlarged view

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

On some vehicles, this may also be referred to as an Engine Coolant Temperature (ECT) sensor.

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 ECM is supplied by the coolant temperature 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 (100,000 ohms at 40ºF/40ºC) and high coolant temperature produces low resistance (70 ohms at 266ºF/130ºC). The ECM supplies a signal of 5 volts to the coolant temperature sensor through a resistor in the ECM and measures the voltage. The voltage will be high when the engine is cold and low when the engine is hot.

For 2.5L engines, the coolant temperature sensor is located on the left side of the cylinder head.

For MFI engines, the coolant temperature sensor is located on the intake manifold water jacket or near (or on) the thermostat housing.

TESTING



See Figures 2 and 3

  1. Remove the ECT sensor from the vehicle.
  2.  
  3. Immerse the tip of the sensor in container of water.
  4.  
  5. Connect a digital ohmmeter to the two terminals of the sensor.
  6.  
  7. Using a calibrated thermometer, compare the resistance of the sensor to the temperature of the water. Refer to the engine coolant sensor temperature vs. resistance illustration.
  8.  
  9. Repeat the test at two other temperature points, heating or cooling the water as necessary.
  10.  
  11. If the sensor does not met specification, it must be replaced.
  12.  



Click image to see an enlarged view

Fig. Fig. 2: Submerge the end of the coolant temperature sensor in cold or hot water and check the resistance



Click image to see an enlarged view

Fig. Fig. 3: Engine Coolant Temperature (ECT) sensor temperature vs. resistance values

REMOVAL & INSTALLATION



See Figures 4, 5, 6 and 7

Click image to see an enlarged view

Fig. Fig. 4: Location of the ECT and related sensors-2.3L engine



Click image to see an enlarged view

Fig. Fig. 5: Engine Coolant Temperature (ECT) sensor location-3.1L (VIN T) engine shown



Click image to see an enlarged view

Fig. Fig. 6: If equipped, as on this 3.1L (VIN M) engine, make sure the tab on the sensor is locked inProperly



Click image to see an enlarged view

Fig. Fig. 7: On the 3.4L engine, you must remove the intake plenum to access the ECT sensor

  1. Relieve the cooling system pressure by removing the radiator cap.
  2.  


CAUTION
Perform this procedure only on a cold engine. Attempting to remove any component that involves working with engine coolant can result in serious burns.

  1. Disconnect the negative battery cable.
  2.  
  3. For 3.8L and 1994-96 3.4L engines, drain the engine coolant into a suitable container.
  4.  


CAUTION
When draining the coolant, keep in mind that cats and dogs are attracted by ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or inPuddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

  1. For 3.1L and 3.8L engines, remove the air intake duct or intercooler-to-intake manifold tube, as applicable.
  2.  
  3. For 1991-93 3.4L engines, remove the intake manifold plenum (upper manifold), as outlined in Engine & Engine Overhaul of this repair guide.
  4.  
  5. For 1994-96 3.4L engines, perform the following
    1. Remove the air cleaner assembly.
    2.  
    3. Remove the rear intake duct and MAF assembly.
    4.  
    5. Remove the exhaust crossover pipe.
    6.  

  6.  
  7. Detach the sensor electrical connector.
  8.  


WARNING
Be careful when handling the coolant temperature sensor. Damage to the sensor will affect proper operation of the fuel injection system.

  1. Remove the threaded temperature sensor from the engine.
  2.  

To install:
  1. Coat the threads of the sensor with sealant 1052080, 9985253 or equivalent.
  2.  

If equipped, make sure the locking tab on the sensor is located within the area shown in the accompanying figure.

  1. Install the sensor in the engine and tighten as follows:
    1. 2.2L engine: 18 ft. lbs. (25 Nm).
    2.  
    3. 2.3L and 2.5L engines: 22 ft. lbs. (30 Nm).
    4.  
    5. 3.1L (VIN T and V), 3.4L and 3.8L engines: 22 ft. lbs. (30 Nm).
    6.  
    7. 3.1L (VIN M) engine: 10 ft. lbs. (14 Nm).
    8.  

  2.  
  3. Attach the sensor electrical connector.
  4.  
  5. For 1994-96 3.4L engines, perform the following:
    1. Install the exhaust crossover pipe.
    2.  
    3. Attach the rear intake duct and install the MAF sensor.
    4.  
    5. Install the air cleaner assembly.
    6.  

  6.  
  7. For 3.1L and 3.8L engines, install the air intake duct or intercooler-to-intake manifold tube, as applicable.
  8.  
  9. If any coolant was lost, fill the cooling system to the proper level with the correct type of coolant.
  10.  
  11. Connect the negative battery cable. Start the engine and check for leaks and proper operation.
  12.  

 
label.common.footer.alt.autozoneLogo