Suzuki Samurai/Sidekick/Tracker 1986-1998 Repair Guide

Intake Air Temperature (IAT) and Air Temperature Sensors (ATS)

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OPERATION



See Figure 1

The Intake Air Temperature (IAT) sensor not used on carbureted engines. Also, it is referred to as the Air Temperature Sensor (ATS) on 1.3L TFI engines.

The Intake Air Temperature (IAT) sensor is a thermistor (a resistor which changes its value based on the temperature it encounters) mounted in the incoming air stream. Low incoming air temperature produces a high resistance, while high temperature causes a low resistance.

The ECM supplies a 5 volt reference signal to the IAT sensor through a resistor in the ECM, and measures the voltage. By measuring the voltage the ECM calculates the temperature of the incoming air. The ECM uses the IAT information to calculate air density, which affects air/fuel mixture. The IAT sensor is used to control air/fuel mixture, spark timing, and delays in the EGR system when the intake air is cold.



Click image to see an enlarged view

Fig. Fig. 1: Intake Air Temperature (IAT) sensor circuit-1996-98 1.8L engines

A failure in the IAT sensor should set a Diagnostic Trouble Code (DTC). Remember that these DTC's indicate a failure somewhere in the component's circuit, so a DTC does not necessarily mean that the sensor itself is bad. Once a DTC is set, the ECM will use an artificial default value for the IAT sensor and some engine performance will return.

The ATS used on 1.3L TFI engines is mounted in the intake manifold. The IAT sensor used on the 1.6L TFI engine is located on the right-hand side of the engine, mounted in the intake manifold below the throttle body. The IAT sensor used on 1.6L and 1.8L MFI engines is mounted in the backside of the air cleaner housing.

TESTING



See Figures 2 and 3

The IAT sensor/ATS may be tested by measuring the temperature-to-resistance values with an ohmmeter. A cold sensor should have a high resistance value, whereas a warm sensor should exhibit a low resistance value.

  1. Perform a visual inspection of the sensor connector to ensure that it is properly engaged, and that there are no bent, corroded, loose or damaged terminals.
  2.  
  3. Remove the sensor from the intake manifold (TFI engines) or from the air cleaner housing (MFI engines).
  4.  
  5. As shown in the accompanying illustration, position the sensor and a thermometer in a container of cold water on a stove.
  6.  



Click image to see an enlarged view

Fig. Fig. 2: Situate the IAT/ATS sensor so that the temperature probe is positioned in a container of cold water, then measure the resistance of the sensor



Click image to see an enlarged view

Fig. Fig. 3: Slowly heat the water up and observe the sensor resistance-the sensor resistance should match the values provided

  1. Using an ohmmeter, measure and note the resistance between the two sensor terminals. Also note the temperature of the water.
  2.  
  3. While observing the ohmmeter and thermometer, slowly heat the water in the container. The resistance of the sensor should smoothly decrease as the water temperature increases, and should match the accompanying chart.
  4.  
  5. If the sensor resistance values match those in the accompanying resistance table, and if the resistance changed smoothly while warming the water, the sensor is good. Otherwise, replace the sensor with a new one.
  6.  
  7. Install the sensor.
  8.  

REMOVAL & INSTALLATION



1.3L and 1.6L TFI Engines
  1. Disconnect the negative battery cable.
  2.  
  3. Detach the wiring harness connector from the sensor.
  4.  
  5. Remove the sensor from the intake manifold.
  6.  

To install:
  1. If the old sensor is going to be reinstalled, clean the sensor threads thoroughly.
  2.  
  3. Apply silicone sealant on, or wrap Teflon® sealing tape around, the sensor threads.
  4.  
  5. Thread the sensor into the intake manifold by hand until finger-tight, then tighten the sensor to 9-12 ft. lbs. (12-17 Nm).
  6.  
  7. Reattach the wiring harness connector to the sensor.
  8.  
  9. Connect the negative battery cable.
  10.  
  11. Start the engine and ensure proper sensor operation.
  12.  

1.6L MFI and 1.8L Engines
  1. Disconnect the negative battery cable.
  2.  
  3. Detach the wiring harness connector from the sensor.
  4.  
  5. Remove the IAT sensor from the air cleaner housing.
  6.  

To install:
  1. Insert the sensor into the air cleaner housing.
  2.  
  3. Reattach the wiring harness connector to the sensor.
  4.  
  5. Connect the negative battery cable.
  6.  
  7. Start the engine and ensure proper IAT sensor operation.
  8.  

 
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