Saturn Coupes/Sedans/Wagons 1991-1998 Repair Guide

Air Temperature Sensor (ATS)

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OPERATION



This sensor is a thermistor type, meaning as the temperature increases, the sensor resistance decreases. It is the same type of sensor as the CTS. The PCM sends a 5 volt reference signal to the sensor and interprets the voltage drop across the sensor to calculate engine intake air temperature.

TESTING



See Figures 1

  1. If a code has been set and the vehicle has not been exposed to temperatures lower than -22°F (-30°), unplug the connector from the sensor and use the chart to check the sensor resistance with an ohmmeter.
  2.  
  3. With the ignition switch ON , check for 5 volts to the sensor at connector terminal A , the tan wire.
  4.  
  5. If using a scan tool connected to the ALDL, the reading should be the same as the actual air temperature with the ignition switch ON .
    1. If the reading is less than -22°F (-30°C), unplug the sensor connector and jumper the PCM terminals together. If the reading goes to above 266°F (130°C), the problem is in the sensor. If the reading does not change or go high enough, the problem is in the wiring or the PCM.
    2.  
    3. If the reading is more than 284°F (140°C), unplug the sensor connector. If the reading goes below -22°F (-30°C), the problem is in the sensor. If it does not change or does not go low enough, the problem is in the wiring or the PCM.
    4.  

  6.  
  7. If a scan tool is available, allow the engine to cool to the ambient temperature overnight, then compare the CTS and ATS readings. Temperatures should be within 4 degrees of each other with the ignition ON and the engine not running.
  8.  



Click image to see an enlarged view

Fig. Fig. 1: Schematic for the air temperature sensor circuit

REMOVAL & INSTALLATION



See Figures 2 and 3

  1. As an added safety precaution, you may wish to disable the air bag(s). refer to Chassis Electrical for the disabling procedures.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Remove the air inlet tube fasteners, then rotate the tube to access the sensor.
  6.  
  7. Using your hand or a pair of pliers, gently squeeze the sides of the sensor electrical connector, then remove the connector from the sensor.
  8.  
  9. Using a 13mm deep well socket, loosen and remove the sensor from the inlet duct.
  10.  

To install:
  1. Install the sensor and tighten to 44 inch lbs. (5 Nm).
  2.  
  3. Attach the sensor electrical connector.
  4.  
  5. Install the air inlet tube using the fasteners.
  6.  
  7. Connect the negative battery cable.
  8.  
  9. If necessary, enable the air bag(s). refer to Chassis Electrical .
  10.  



Click image to see an enlarged view

Fig. Fig. 2: Air temperature sensor installation-DOHC engine



Click image to see an enlarged view

Fig. Fig. 3: Air temperature sensor installation-SOHC engine

 
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