CTS 2003-2005

Testing

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There are a few items you should check before beginning more extensive testing.



Check for poor connection at the PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal-to-wire connections.
 
Look for a damaged harness or damaged wiring going to the ECT sensor, especially if heavy work has recently been done where the connector could have been damaged.
 

Sensor Installed In Vehicle





Click image to see an enlarged view

Fig. ECT sensor resistance value chart

  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.  

Sensor Removed From Vehicle



  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.  

 
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