Vue 2002-2005

EGR Valve Position Sensor

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Operation



The Exhaust Gas Recirculation (EGR) system is used to reduce the amount of nitrogen oxide (NOx) emission levels caused by combustion temperatures exceeding 1,500°F (816°C). It does this by introducing small amounts of exhaust gas back into the combustion chamber. The exhaust gas absorbs a portion of the thermal energy produced by the combustion process and thus decreases combustion temperature. The EGR system will only operate under specific temperature, Barometric Pressure (BARO) and engine load conditions in order to prevent drivability concerns and to increase engine performance.

The PCM calculates the amount of EGR needed based on the following inputs:



The Engine Coolant Temperature (ECT) sensor
 
The Intake Air Temperature (IAT) sensor
 
The Barometric Pressure (BARO)
 
The Manifold Absolute Pressure (MAP) sensor
 
The Throttle Position (TP) sensor
 
The Mass Air Flow (MAF) sensor
 

The control module tests the EGR system during deceleration. The control module does this by momentarily commanding the EGR valve to open while monitoring the signal circuit of the Manifold Absolute Pressure (MAP) sensor. When the EGR valve is opened, the control module will expect to see a predetermined increase in MAP. If the expected increase in MAP is not detected, the control module records the amount of MAP difference that was detected and adjusts a calibrated fail counter towards a calibrated fail threshold level. The number of EGR flow test counts required to exceed the fail threshold may vary according to the amount of detected EGR flow error.

The EGR Valve Position (EVP) sensor is monitored by the control module. The 5-volt reference circuit, the low reference circuit, and the EVP signal circuit are used by the control module to determine the EGR valve position. The control module compares the EVP sensor parameter with the desired EGR position parameter when the valve is commanded open or closed.

The control module controls the EGR valve with a solid state device called a driver. The driver supplies the EGR solenoid with 12 volts that is Pulse Width Modulated (PWM) through the EGR solenoid high control circuit. A ground path is provided by the control module through the EGR solenoid low control circuit. The driver has the ability to detect an electrical malfunction on the EGR solenoid control circuits.

When the ignition switch is turned ON, the control module records the EGR learned minimum position. The control module compares the EGR learned minimum position parameter to the EVP parameter.

The control module will only allow one EGR flow test during an ignition cycle. To aid in verifying a repair, the control module will allow 9-16 EGR flow test counts during the first ignition cycle following a code clear event or a battery disconnect.

Removal & Installation



3.5L Engine
  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Turn the ignition OFF.
  4.  
  5. Disconnect the Exhaust Gas Recirculation (EGR) valve electrical connector.
  6.  
  7. Remove the EGR valve retaining nuts.
  8.  
  9. Remove the EGR valve assembly.
  10.  
  11. Remove the gasket.
  12.  
  13. Clean the EGR valve mating surface.
  14.  

To install:

  1. Install the EGR valve with a new gasket to the engine.
  2.  
  3. Install the EGR valve nuts. Tighten the nuts to 16 ft. lbs. (22 Nm).
  4.  
  5. Connect the EGR valve electrical connector.
  6.  

Testing



  1. With the ignition ON and the engine OFF, command the EGR from 0-90 percent. The Exhaust Gas Recirculation (EGR) position sensor parameter should remain within 3 percent of the desired EGR position parameter through the entire range.
  2.  
  3. With the ignition OFF, disconnect the EGR valve harness connector.
  4.  
  5. Turn the ignition ON, connect a test lamp between B and A. The test lamp should illuminate.
    1. If the test lamp does not illuminate, test the EGR low control circuit for an open/high resistance.
    2.  
    3. If the circuit tests normal, replace the ECM.

      Click image to see an enlarged view

      Fig. EGR connector end view-3.5L engine

    4.  

  6.  
  7. Connect a test lamp between the EGR control circuit and a ground. Command the EGR valve from 0-90 percent and exit the EGR solenoid output control. The test lamp should turn ON when commanded between 10-90 percent and turn OFF when commanded to 0 percent.
    1. If the test lamp is ON when commanded to 0 percent, test the EGR high control circuit for a short to voltage.
    2.  
    3. If the circuit tests normal, replace the ECM.
    4.  
    5. If the test lamp is always OFF while commanding the EGR valve from 0-90 percent, test the EGR high control circuit for an open, high resistance, or a short to ground.
    6.  
    7. If the circuit tests normal, replace the ECM.
    8.  

  8.  
  9. If all circuits test normal, replace the EGR valve.

    Click image to see an enlarged view

    Fig. EGR linear valve cut-away view

  10.  

 
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