Ram Truck 1500, 2500 & 3500 (2006-2008)

Intake Air Temperature Sensor

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Operation



3.7L, 4.7L & 5.7L Engines

The Intake Air Temperature (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 5-volt 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 resistance values of the IAT sensor are the same as for the Engine Coolant Temperature (ECT) sensor.

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).
 

5.9L & 6.7L Engines

The combination, dual function Intake Manifold Air Temperature Sensor/MAP Sensor is installed into the top of the intake manifold with the sensor element extending into the air stream.

The IAT portion of the sensor provides an input voltage to the Engine Control Module (ECM) indicating intake manifold air temperature. The MAP portion of the sensor provides an input voltage to the ECM indicating turbocharger boost pressure.

Removal & Installation



3.7L, 4.7L & 5.7L Engines
  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Disconnect the electrical connector from IAT sensor.
  4.  
  5. Clean any dirt from intake tube at the sensor base.
  6.  
  7. Gently lift on small plastic release tab and rotate sensor about 1 / 4 turn counter-clockwise for removal.
  8.  
  9. Check the condition of IAT sensor O-ring.
  10.  

To install:

  1. Clean sensor mounting hole in air intake tube.
  2.  
  3. Position sensor into air intake tube and rotate clockwise until past release tab.
  4.  
  5. Install the electrical connector.
  6.  

5.9L Engine
  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Clean the area around the sensor.
  4.  
  5. Disconnect the electrical connector from IAT/MAP sensor.
  6.  
  7. Remove two T-15 Torx headed screws.
  8.  
  9. Remove the sensor from the intake manifold.
  10.  
  11. Check condition of sensor O-ring.

    Click image to see an enlarged view

    Fig. IAT/MAP sensor 5.9L engine

  12.  

To install:

  1. Lubricate the sensor o-ring and sensor hole in the intake manifold cover with clean engine oil.
  2.  
  3. Clean sensor mounting area at intake manifold.
  4.  
  5. Position the sensor into intake manifold.
  6.  
  7. Install and tighten 2 sensor mounting screws to 1 Nm 9 in. lbs. (1 Nm).
  8.  
  9. Connect the electrical connector to the sensor.
  10.  

6.7L Engine
  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Clean the area around sensor.
  4.  
  5. Disconnect the electrical connector from IAT/MAP sensor.
  6.  
  7. Remove the mounting screw.
  8.  
  9. Remove the IAT/MAP sensor from manifold.
  10.  
  11. Check condition of sensor O-ring.
  12.  

To install:

  1. Clean sensor mounting area at intake manifold.
  2.  
  3. Lubricate the sensor O-ring and sensor mounting hole in intake manifold with clean engine oil.
  4.  
  5. Position the sensor into the intake manifold.
  6.  
  7. Install and tighten sensor mounting screw to 1 Nm 9 in. lbs. (1 Nm).
  8.  
  9. Connect the electrical connector to sensor.
  10.  

Testing



3.7L, 4.7L & 5.7L Engines
  1. Turn the ignition off.
  2.  
  3. Disconnect the Intake Air Temperature (IAT) Sensor harness connector. Turn the ignition on.
  4.  
  5. Install a scan tool, read the IAT sensor voltage.
  6.  
  7. The sensor voltage should be approximately 5.0 volts (plus or minus .1 volt) with the connector disconnected. If not repair the open in the (K21) IAT Signal circuit.
  8.  
  9. If the voltage reading was okay connect a jumper wire between the (K21) IAT Signal circuit and the (K900) Sensor ground circuit in the IAT Sensor harness connector.
  10.  
  11. With the scan tool, read the IAT voltage.
  12.  
  13. The sensor voltage should be approximately 0.0 volts (plus or minus .1 volt) with the jumper wire in place. If the readings are as stated, verify that there is good pin to terminal contact in the sensor and Powertrain Control Module (PCM) connectors. Replace the IAT sensor if no problems were found with the connectors.

    Click image to see an enlarged view

    Fig. Intake Air Temperature (IAT) Sensor, PCM harness connectors and wiring diagram

  14.  

5.9L & 6.7L Engines
  1. Remove the temperature sensor and reconnect the wiring to the sensor.
  2.  
  3. Turn on the ignition switch, engine off.
  4.  
  5. With the scan tool in sensors, monitor the Intake Air Temperature (IAT).
  6.  
  7. While heating the sensor with an external heat source (DO NOT USE OPEN FLAME).
  8.  
  9. The reading from the sensor should increase at least -15° C (5° F) on the scan tool.
  10.  
  11. If not replace the intake air temperature sensor.
  12.  

 
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