Lexus Car ES, IS, LS 1998-06

Intake Air Temperature (IAT) Sensor

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Operation



The 2 wire Intake Manifold Air Temperature (IAT) sensor is installed in the intake manifold with the sensor element extending into the air stream.

The IAT sensor is a two-wire Negative Thermal Coefficient (NTC) sensor. Meaning, as intake manifold temperature increases, resistance (voltage) in the sensor decreases. As temperature decreases, resistance (voltage) in the sensor increases.

The IAT sensor provides an input voltage to the Powertrain Control Module (PCM) indicating the density of the air entering the intake manifold based upon intake manifold temperature. At key-on, a 5volt power circuit is supplied to the sensor from the PCM. The sensor is grounded at the PCM through a low-noise, sensor-return circuit.

The PCM uses this input to calculate the following:



Injector pulse-width
 
Adjustment of spark timing (to help prevent spark knock with high intake manifold air-charge temperatures)
 

The resistance values of the IAT sensor are the same as for the Engine Coolant Temperature (ECT) sensor.

Removal & Installation



4.0L Engine

The Intake Manifold Air Temperature (IAT) sensor is installed into the intake manifold plenum near the front of the throttle body.

  1. Install sensor into intake manifold. Tighten sensor to 28 Nm (20 ft. lbs.) torque.
  2.  
  3. Connect electrical connector to sensor.
  4.  

4.7L

The Intake Manifold Air Temperature (IAT) sensor is located on the left side of the intake manifold.

Threaded Type Sensor

  1. Disconnect electrical connector from sensor.
  2.  
  3. Remove sensor from intake manifold.
  4.  

Snap-In Type Sensor

  1. Disconnect electrical connector from IAT sensor.
  2.  
  3. Clean dirt from intake manifold at sensor base.
  4.  
  5. Gently lift on small plastic release tab and rotate sensor about 1/4 turn counter-clockwise for Removal & Installation.
  6.  
  7. Check condition of sensor O-ring.

    Click image to see an enlarged view

    Fig.



    Click image to see an enlarged view

    Fig.

  8.  

To Install:

Threaded Type Sensor

  1. Install sensor into intake manifold. Tighten sensor to 28 Nm (20 ft. lbs.) torque.
  2.  
  3. Connect electrical connector to sensor.
  4.  

Snap-In Type Sensor

  1. Check condition of sensor O-ring.
  2.  
  3. Clean sensor mounting hole in intake manifold.
  4.  
  5. Position sensor into intake manifold and rotate clockwise until past release tab.
  6.  
  7. Install electrical connector.
  8.  

 
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