Mitsubishi Car 1999-05

Intake Air Temperature (IAT) Sensor

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Operation





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Fig. The IAT sensor tip is visible when looking into the MAF sensor

The Intake Air Temperature (IAT) sensor determines the air temperature entering the intake manifold. Resistance changes in response to the ambient air temperature. The sensor has a negative temperature coefficient. As the temperature of the sensor rises the resistance across the sensor decreases. This provides a signal to the PCM indicating the temperature of the incoming air charge. This sensor helps the PCM to determine spark timing and air/fuel ratio. Information from this sensor is added to the pressure sensor information to calculate the air mass being sent to the cylinders. The IAT receives a 5-volt reference signal and the signal return is based upon the change in the measured resistance due to temperature.

Approximately 5-volts are applied to the Intake Air Temperature (IAT) Sensor output terminal from the PCM via the resistor in the PCM. The ground terminal is grounded with PCM. The sensor is a negative temperature coefficient type of resistor. When the intake air temperature rises, the resistance decreases. The sensor output voltage increases when the resistance increases and decreases when the resistance decreases.

Approximately 5-volts are applied to the Intake Air Temperature (IAT) Sensor output terminal from the PCM via the resistor in the PCM. The ground terminal is grounded with PCM. The sensor is a negative temperature coefficient type of resistor. When the intake air temperature rises, the resistance decreases. The sensor output voltage increases when the resistance increases and decreases when the resistance decreases.

Approximately 5-volts are applied to the Intake Air Temperature (IAT) Sensor output terminal from the PCM via the resistor in the PCM. The ground terminal is grounded with PCM. The sensor is a negative temperature coefficient type of resistor. When the intake air temperature rises, the resistance decreases. The sensor output voltage increases when the resistance increases and decreases when the resistance decreases.

Approximately 5-volts are applied to the Intake Air Temperature (IAT) Sensor output terminal from the PCM via the resistor in the PCM. The ground terminal is grounded with PCM. The sensor is a negative temperature coefficient type of resistor. When the intake air temperature rises, the resistance decreases. The sensor output voltage increases when the resistance increases and decreases when the resistance decreases.

Approximately 5-volts are applied to the Intake Air Temperature (IAT) Sensor output terminal from the PCM via the resistor in the PCM. The ground terminal is grounded with PCM. The sensor is a negative temperature coefficient type of resistor. When the intake air temperature rises, the resistance decreases. The sensor output voltage increases when the resistance increases and decreases when the resistance decreases.

Approximately 5-volts are applied to the Intake Air Temperature (IAT) Sensor output terminal from the PCM via the resistor in the PCM. The ground terminal is grounded with PCM. The sensor is a negative temperature coefficient type of resistor. When the intake air temperature rises, the resistance decreases. The sensor output voltage increases when the resistance increases and decreases when the resistance decreases.

Removal & Installation



The IAT sensor is part of the Mass Air Flow (MAF) sensor. The IAT sensor cannot be replaced separately. Refer to MAF sensor removal and installation in this section.

  1. Disconnect the negative battery cable.
  2.  
  3. Replacing the sensor requires disconnecting the electrical connector, then carefully removing the lid of the air filter housing.
    NOTE
    Handle the sensor assembly carefully, protecting it from impact, extremes of temperature and/or exposure to shop chemicals.

  4.  
  5. Installation is the reverse of the removal procedure.
  6.  

  1. Disconnect the negative battery cable.
  2.  
  3. Replacing the sensor requires disconnecting the electrical connector, then carefully removing the lid of the air filter housing.
    NOTE
    Handle the sensor assembly carefully, protecting it from impact, extremes of temperature and/or exposure to shop chemicals.

  4.  
  5. Installation is the reverse of the removal procedure.
  6.  

  1. Disconnect the negative battery cable.
  2.  
  3. Replacing the sensor requires disconnecting the electrical connector, then carefully removing the lid of the air filter housing.
    NOTE
    Handle the sensor assembly carefully, protecting it from impact, extremes of temperature and/or exposure to shop chemicals.

  4.  
  5. Installation is the reverse of the removal procedure.
  6.  

  1. Disconnect the negative battery cable.
  2.  
  3. Replacing the sensor requires disconnecting the electrical connector, then carefully removing the lid of the air filter housing.
    NOTE
    Handle the sensor assembly carefully, protecting it from impact, extremes of temperature and/or exposure to shop chemicals.

  4.  
  5. Installation is the reverse of the removal procedure.
  6.  

  1. Disconnect the negative battery cable.
  2.  
  3. Replacing the sensor requires disconnecting the electrical connector, then carefully removing the lid of the air filter housing.
    NOTE
    Handle the sensor assembly carefully, protecting it from impact, extremes of temperature and/or exposure to shop chemicals.

  4.  
  5. Installation is the reverse of the removal procedure.
  6.  

  1. Disconnect the negative battery cable.
  2.  
  3. Replacing the sensor requires disconnecting the electrical connector, then carefully removing the lid of the air filter housing.
    NOTE
    Handle the sensor assembly carefully, protecting it from impact, extremes of temperature and/or exposure to shop chemicals.

  4.  
  5. Installation is the reverse of the removal procedure.
  6.  

Testing





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Fig. Testing the resistance of the IAT sensor across the two sensor pins



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



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Fig. IAT sensor terminal identification-1990-93 Galant



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Fig. IAT sensor terminal identification-2.4L engines



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Fig. Measure the intake air temperature sensor resistance while heating it with a hair drier

  1. Detach the air flow sensor electrical connector.
  2.  
  3. Measure the resistance between terminals No. 4 and No. 6 of the electrical connector, except on the 2.0L DOHC turbo engine.
  4.  
  5. If equipped with the 2.0L DOHC turbo engine, measure the resistance between terminals No. 6 and No. 8 of the sensor electric connector.
  6.  
  7. Compare test readings to the following specifications:
  8.  

  1. Sensor temperature of 32°F (0°C)-5.3-6.7 kilo-ohms
  2.  
  3. Sensor temperature of 68°F (20°C)-2.3-3.0 kilo-ohms
  4.  
  5. Sensor temperature of 176°F (80°C)-0.30-0.42 kilo-ohms
  6.  

  1. Measure the sensor resistance while heating the sensor area with a hair dryer. As the temperature of the sensor increases, sensor resistance should become smaller.
  2.  
  3. If the measured resistance deviates from the standard value or the resistance remains unchanged, replace the air flow sensor assembly.
  4.  

  1. Disconnect the sensor connector.
  2.  
  3. Measure the resistance between the sensor side connector terminals 1 and 4.
  4.  
  5. Standard values are: 13-17 kohms at -4°F, 5.3-6.7 kohms at 32°F, 2.3-3.0 kohms at 68°F, 1.0-1.5 kohms at 104°F, 0.56-0.76 kohms at 140°F, 0.30-0.45 kohms at 176°F
  6.  
  7. Measure resistance while heating the sensor using warm, dry air. As the temperature rises, the resistance value should drop. If within specifications, replace the ECM or PCM.
    NOTE
    Check that the circuit is not Open circuit.

  8.  
  9. If no continuity, replace the Mass Air Flow (MAF) Sensor.
  10.  
  11. If continuity, turn the ignition switch to "ON" position and measure the voltage between terminal 1 and ground on the harness side of the sensor connector. Voltage should be between 4.5 and 4.9 volts.
  12.  
  13. Turn the ignition switch to "LOCK" (OFF) position and check for the resistance between terminal 4 and ground. Resistance should be less than 2 ohm.
  14.  
  15. If any check above does not meet the specifications, check connectors and wiring between the sensor and ECM/PCM. If ok, replace ECM/PCM.
  16.  

  1. Disconnect the sensor connector.
  2.  
  3. Measure the resistance between the sensor side connector terminals 1 and 4.
  4.  
  5. Standard values are: 13-17 kohms at -4°F, 5.3-6.7 kohms at 32°F, 2.3-3.0 kohms at 68°F, 1.0-1.5 kohms at 104°F, 0.56-0.76 kohms at 140°F, 0.30-0.45 kohms at 176°F
  6.  
  7. Measure resistance while heating the sensor using warm, dry air. As the temperature rises, the resistance value should drop. If within specifications, replace the ECM or PCM.
    NOTE
    Check that the circuit is not Open circuit.

  8.  
  9. If no continuity, replace the Mass Air Flow (MAF) Sensor.
  10.  
  11. If continuity, turn the ignition switch to "ON" position and measure the voltage between terminal 1 and ground on the harness side of the sensor connector. Voltage should be between 4.5 and 4.9 volts.
  12.  
  13. Turn the ignition switch to "LOCK" (OFF) position and check for the resistance between terminal 4 and ground. Resistance should be less than 2 ohm.
  14.  
  15. If any check above does not meet the specifications, check connectors and wiring between the sensor and ECM/PCM. If ok, replace ECM/PCM.
  16.  

  1. Disconnect the sensor connector.
  2.  
  3. Measure the resistance between the sensor side connector terminals 1 and 4.
  4.  
  5. Standard values are: 13-17 kohms at -4°F, 5.3-6.7 kohms at 32°F, 2.3-3.0 kohms at 68°F, 1.0-1.5 kohms at 104°F, 0.56-0.76 kohms at 140°F, 0.30-0.45 kohms at 176°F
  6.  
  7. Measure resistance while heating the sensor using warm, dry air. As the temperature rises, the resistance value should drop. If within specifications, replace the ECM or PCM.
    NOTE
    Check that the circuit is not Open circuit.

  8.  
  9. If no continuity, replace the Mass Air Flow (MAF) Sensor.
  10.  
  11. If continuity, turn the ignition switch to "ON" position and measure the voltage between terminal 1 and ground on the harness side of the sensor connector. Voltage should be between 4.5 and 4.9 volts.
  12.  
  13. Turn the ignition switch to "LOCK" (OFF) position and check for the resistance between terminal 4 and ground. Resistance should be less than 2 ohm.
  14.  
  15. If any check above does not meet the specifications, check connectors and wiring between the sensor and ECM/PCM. If ok, replace ECM/PCM.
  16.  

  1. Disconnect the sensor connector.
  2.  
  3. Measure the resistance between the sensor side connector terminals 1 and 4.
  4.  
  5. Standard values are: 13-17 kohms at -4°F, 5.3-6.7 kohms at 32°F, 2.3-3.0 kohms at 68°F, 1.0-1.5 kohms at 104°F, 0.56-0.76 kohms at 140°F, 0.30-0.45 kohms at 176°F
  6.  
  7. Measure resistance while heating the sensor using warm, dry air. As the temperature rises, the resistance value should drop. If within specifications, replace the ECM or PCM.
    NOTE
    Check that the circuit is not Open circuit.

  8.  
  9. If no continuity, replace the Mass Air Flow (MAF) Sensor.
  10.  
  11. If continuity, turn the ignition switch to "ON" position and measure the voltage between terminal 1 and ground on the harness side of the sensor connector. Voltage should be between 4.5 and 4.9 volts.
  12.  
  13. Turn the ignition switch to "LOCK" (OFF) position and check for the resistance between terminal 4 and ground. Resistance should be less than 2 ohm.
  14.  
  15. If any check above does not meet the specifications, check connectors and wiring between the sensor and ECM/PCM. If ok, replace ECM/PCM.
  16.  

  1. Disconnect the sensor connector.
  2.  
  3. Measure the resistance between the sensor side connector terminals 1 and 4.
  4.  
  5. Standard values are: 13-17 kohms at -4°F, 5.3-6.7 kohms at 32°F, 2.3-3.0 kohms at 68°F, 1.0-1.5 kohms at 104°F, 0.56-0.76 kohms at 140°F, 0.30-0.45 kohms at 176°F
  6.  
  7. Measure resistance while heating the sensor using warm, dry air. As the temperature rises, the resistance value should drop. If within specifications, replace the ECM or PCM.
    NOTE
    Check that the circuit is not Open circuit.

  8.  
  9. If no continuity, replace the Mass Air Flow (MAF) Sensor.
  10.  
  11. If continuity, turn the ignition switch to "ON" position and measure the voltage between terminal 1 and ground on the harness side of the sensor connector. Voltage should be between 4.5 and 4.9 volts.
  12.  
  13. Turn the ignition switch to "LOCK" (OFF) position and check for the resistance between terminal 4 and ground. Resistance should be less than 2 ohm.
  14.  
  15. If any check above does not meet the specifications, check connectors and wiring between the sensor and ECM/PCM. If ok, replace ECM/PCM.
  16.  

  1. Disconnect the sensor connector.
  2.  
  3. Measure the resistance between the sensor side connector terminals 1 and 4.
  4.  
  5. Standard values are: 13-17 kohms at -4°F, 5.3-6.7 kohms at 32°F, 2.3-3.0 kohms at 68°F, 1.0-1.5 kohms at 104°F, 0.56-0.76 kohms at 140°F, 0.30-0.45 kohms at 176°F
  6.  
  7. Measure resistance while heating the sensor using warm, dry air. As the temperature rises, the resistance value should drop. If within specifications, replace the ECM or PCM.
    NOTE
    Check that the circuit is not Open circuit.

  8.  
  9. If no continuity, replace the Mass Air Flow (MAF) Sensor.
  10.  
  11. If continuity, turn the ignition switch to "ON" position and measure the voltage between terminal 1 and ground on the harness side of the sensor connector. Voltage should be between 4.5 and 4.9 volts.
  12.  
  13. Turn the ignition switch to "LOCK" (OFF) position and check for the resistance between terminal 4 and ground. Resistance should be less than 2 ohm.
  14.  
  15. If any check above does not meet the specifications, check connectors and wiring between the sensor and ECM/PCM. If ok, replace ECM/PCM.
  16.  

 
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