Mitsubishi Car 1999-05

Testing

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The coolant temperature sending unit is used to operate the temperature gauge. Do not confuse this sending unit with the other switches or sensors used to signal the engine control unit or air conditioning regarding temperature of the coolant. Usually, these other units are mounted near the coolant temperature sensor used for engine control.

  1. Disconnect the sensor connector and measure at the harness side.
  2.  
  3. Turn the ignition switch to the "ON" position.
  4.  
  5. Measure the voltage between terminal 1 and ground. Voltage should be between 4.5 and 4.9 volts.
  6.  
  7. Turn the ignition switch to the "LOCK" (OFF) position.
  8.  
  9. Check for the resistance between terminal 2 and ground. Resistance should be less than 2 ohm.
  10.  
  11. If any check above does not meet the specifications, check connectors and wiring between the sensor and ECM/PCM. If ok, replace ECM/PCM.
  12.  
  13. If all checks above meet the specifications, measure the resistance between the sensor side connector terminals 1 and 2. There should be resistance (50-72 kohms).
    NOTE
    Check that the circuit is not open circuit.

  14.  
  15. If no continuity, replace the sensor.
  16.  
  17. If sensor has continuity, remove the sensor.
  18.  
  19. With the temperature sensing portion of sensor immersed in hot water, check resistance.
  20.  
  21. Standard values are: 5.1-6.5 kohms at 32°F, 2.1-2.7 kohms at 68°F, 0.9-1.3 kohms [at 40°C (68°F), 0.26-0.36 kohms [at 80°C (176°F)
  22.  
  23. If not within specifications, replace the sensor.
  24.  

  1. Disconnect the sensor connector and measure at the harness side.
  2.  
  3. Turn the ignition switch to the "ON" position.
  4.  
  5. Measure the voltage between terminal 1 and ground. Voltage should be between 4.5 and 4.9 volts.
  6.  
  7. Turn the ignition switch to the "LOCK" (OFF) position.
  8.  
  9. Check for the resistance between terminal 2 and ground. Resistance should be less than 2 ohm.
  10.  
  11. If any check above does not meet the specifications, check connectors and wiring between the sensor and ECM/PCM. If ok, replace ECM/PCM.
  12.  
  13. If all checks above meet the specifications, measure the resistance between the sensor side connector terminals 1 and 2. There should be resistance (50-72 kohms).
    NOTE
    Check that the circuit is not open circuit.

  14.  
  15. If no continuity, replace the sensor.
  16.  
  17. If sensor has continuity, remove the sensor.
  18.  
  19. With the temperature sensing portion of sensor immersed in hot water, check resistance.
  20.  
  21. Standard values are: 5.1-6.5 kohms at 32°F, 2.1-2.7 kohms at 68°F, 0.9-1.3 kohms [at 40°C (68°F), 0.26-0.36 kohms [at 80°C (176°F)
  22.  
  23. If not within specifications, replace the sensor.
  24.  

  1. Disconnect the sensor connector and measure at the harness side.
  2.  
  3. Turn the ignition switch to the "ON" position.
  4.  
  5. Measure the voltage between terminal 1 and ground. Voltage should be between 4.5 and 4.9 volts.
  6.  
  7. Turn the ignition switch to the "LOCK" (OFF) position.
  8.  
  9. Check for the resistance between terminal 2 and ground. Resistance should be less than 2 ohm.
  10.  
  11. If any check above does not meet the specifications, check connectors and wiring between the sensor and ECM/PCM. If ok, replace ECM/PCM.
  12.  
  13. If all checks above meet the specifications, measure the resistance between the sensor side connector terminals 1 and 2. There should be resistance (50-72 kohms).
    NOTE
    Check that the circuit is not open circuit.

  14.  
  15. If no continuity, replace the sensor.
  16.  
  17. If sensor has continuity, remove the sensor.
  18.  
  19. With the temperature sensing portion of sensor immersed in hot water, check resistance.
  20.  
  21. Standard values are: 5.1-6.5 kohms at 32°F, 2.1-2.7 kohms at 68°F, 0.9-1.3 kohms [at 40°C (68°F), 0.26-0.36 kohms [at 80°C (176°F)
  22.  
  23. If not within specifications, replace the sensor.
  24.  

  1. Disconnect the sensor connector and measure at the harness side.
  2.  
  3. Turn the ignition switch to the "ON" position.
  4.  
  5. Measure the voltage between terminal 1 and ground. Voltage should be between 4.5 and 4.9 volts.
  6.  
  7. Turn the ignition switch to the "LOCK" (OFF) position.
  8.  
  9. Check for the resistance between terminal 2 and ground. Resistance should be less than 2 ohm.
  10.  
  11. If any check above does not meet the specifications, check connectors and wiring between the sensor and ECM/PCM. If ok, replace ECM/PCM.
  12.  
  13. If all checks above meet the specifications, measure the resistance between the sensor side connector terminals 1 and 2. There should be resistance (50-72 kohms).
    NOTE
    Check that the circuit is not open circuit.

  14.  
  15. If no continuity, replace the sensor.
  16.  
  17. If sensor has continuity, remove the sensor.
  18.  
  19. With the temperature sensing portion of sensor immersed in hot water, check resistance.
  20.  
  21. Standard values are: 5.1-6.5 kohms at 32°F, 2.1-2.7 kohms at 68°F, 0.9-1.3 kohms [at 40°C (68°F), 0.26-0.36 kohms [at 80°C (176°F)
  22.  
  23. If not within specifications, replace the sensor.
  24.  

  1. Disconnect the sensor connector and measure at the harness side.
  2.  
  3. Turn the ignition switch to the "ON" position.
  4.  
  5. Measure the voltage between terminal 1 and ground. Voltage should be between 4.5 and 4.9 volts.
  6.  
  7. Turn the ignition switch to the "LOCK" (OFF) position.
  8.  
  9. Check for the resistance between terminal 2 and ground. Resistance should be less than 2 ohm.
  10.  
  11. If any check above does not meet the specifications, check connectors and wiring between the sensor and ECM/PCM. If ok, replace ECM/PCM.
  12.  
  13. If all checks above meet the specifications, measure the resistance between the sensor side connector terminals 1 and 2. There should be resistance (50-72 kohms).
    NOTE
    Check that the circuit is not open circuit.

  14.  
  15. If no continuity, replace the sensor.
  16.  
  17. If sensor has continuity, remove the sensor.
  18.  
  19. With the temperature sensing portion of sensor immersed in hot water, check resistance.
  20.  
  21. Standard values are: 5.1-6.5 kohms at 32°F, 2.1-2.7 kohms at 68°F, 0.9-1.3 kohms [at 40°C (68°F), 0.26-0.36 kohms [at 80°C (176°F)
  22.  
  23. If not within specifications, replace the sensor.
  24.  

  1. Disconnect the sensor connector and measure at the harness side.
  2.  
  3. Turn the ignition switch to the "ON" position.
  4.  
  5. Measure the voltage between terminal 1 and ground. Voltage should be between 4.5 and 4.9 volts.
  6.  
  7. Turn the ignition switch to the "LOCK" (OFF) position.
  8.  
  9. Check for the resistance between terminal 2 and ground. Resistance should be less than 2 ohm.
  10.  
  11. If any check above does not meet the specifications, check connectors and wiring between the sensor and ECM/PCM. If ok, replace ECM/PCM.
  12.  
  13. If all checks above meet the specifications, measure the resistance between the sensor side connector terminals 1 and 2. There should be resistance (50-72 kohms).
    NOTE
    Check that the circuit is not open circuit.

  14.  
  15. If no continuity, replace the sensor.
  16.  
  17. If sensor has continuity, remove the sensor.
  18.  
  19. With the temperature sensing portion of sensor immersed in hot water, check resistance.
  20.  
  21. Standard values are: 5.1-6.5 kohms at 32°F, 2.1-2.7 kohms at 68°F, 0.9-1.3 kohms [at 40°C (68°F), 0.26-0.36 kohms [at 80°C (176°F)
  22.  
  23. If not within specifications, replace the sensor.
  24.  

Gauge Check



  1. Detach the engine coolant gauge sending unit electrical connector.
  2.  
  3. Connect a suitable test light (12V-3.4W) between the harness side connector and the ground.
  4.  
  5. Turn the ignition switch to the ON position.
  6.  
  7. Check the condition of the test light and gauge as follows:
  8.  

  1. If all components are operating properly, the test light should illuminate and the gauge needle should move.
  2.  
  3. If the test light is illuminated and the gauge needle does not move, replace the coolant temperature gauge.
  4.  
  5. If the test light is illuminated and the gauge needle does not move, check the fuse for a broken wire, or resistance between the gauge terminals
  6.  
  7. If the test light is not illuminated and the gauge is not moving, check, then replace the wiring harness, if necessary.
  8.  

Sender Check



  1. Drain the engine coolant to a level below the coolant temperature sending unit.
  2.  
  3. Disconnect the sending unit wiring harness and remove the coolant temperature sending unit.
  4.  
  5. Place the sending unit tip in a pan of warm water. Use a thermometer to measure the water temperature.
  6.  
  7. Measure the resistance across the sending unit terminals while the sending unit is in the water.
  8.  



Click image to see an enlarged view

Fig. Place the sending unit in water and measure the resistance

  1. Note the ohm reading and compare to the following specifications:
  2.  


    Water temperature of 68°F (20°C)-2.21-2.69 kilo-ohms resistance
     
    Water temperature of 158°F (70°C)-90.5-117.5 ohms resistance
     
    Water temperature of 176°F (80°C)-264-328 ohms resistance.
     


If the resistance is not approximately accurate for the temperature, the sending unit must be replaced.

  1. Drain the engine coolant to a level below the coolant temperature sending unit.
  2.  
  3. Disconnect the sending unit wiring harness and remove the coolant temperature sending unit.
  4.  
  5. Place the sending unit tip in a pan of warm water. Use a thermometer to measure the water temperature.
  6.  
  7. Measure the resistance across the sending unit terminals while the sending unit is in the water.

    Click image to see an enlarged view

    Fig. Place the sending unit in water and measure the resistance

  8.  
  9. Note the ohm reading and compare to the following specifications:

    Water temperature of 68°F (20°C)-2.21-2.69 kilo-ohms resistance
     
    Water temperature of 158°F (70°C)-90.5-117.5 ohms resistance
     
    Water temperature of 176°F (80°C)-264-328 ohms resistance.
     

  10.  

If the resistance is not approximately accurate for the temperature, the sending unit must be replaced.

Sensor





Click image to see an enlarged view

Fig. Unplug the ECT sensor electrical connector



Click image to see an enlarged view

Fig. Test the resistance of the ECT sensor across the two sensor pins



Click image to see an enlarged view

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



Click image to see an enlarged view

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

  1. Drain the engine coolant to a level below the intake manifold.
  2.  
  3. Disconnect the sensor wiring harness and remove the coolant temperature sensor from the engine.
  4.  
  5. Place the temperature sensing portion of the sensor into a pan of hot water. Use a thermometer to monitor the water temperature.
  6.  
  7. Measure the resistance across the sensor terminals while the sensor is in the water. Compare obtained reading to specifications:
  8.  

  1. Water temperature of 32°F (0°C)-5.1-6.5 kilo-ohms present
  2.  
  3. Water temperature of 68°F (20°C)-2.1-2.7 kilo-ohms present
  4.  
  5. Water temperature of 104°F (40°C)-0.9-1.3 kilo-ohms present
  6.  
  7. Water temperature of 176°F (80°C)-0.26-0.36 kilo-ohms present
  8.  

  1. If the resistance differs greatly from standard value, replace the sensor.
  2.  

 
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