Ram 1500, 2500, 3500, 2WD and 4WD, 2001-2005

Manifold Absolute Pressure Sensor

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Operation



The Manifold Absolute Pressure (MAP) sensor measures the pressure inside the intake manifold, by measuring the vacuum level. It sends a voltage signal to the ECM in relation to the pressure inside the manifold, which varies according to engine load and altitude. The ECM uses this signal to adjust the air/fuel ratio.

The Manifold Absolute Pressure (MAP) sensor measures the pressure inside the intake manifold, by measuring the vacuum level. It sends a voltage signal to the ECM in relation to the pressure inside the manifold, which varies according to engine load and altitude. The ECM uses this signal to adjust the air/fuel ratio.

Testing




WARNING
Testing the wiring harness with the ECM still connected can cause serious damage to the processor. ALWAYS disconnect the ECM before testing the wiring harness, unless instructed otherwise.

  1. Remove the engine cover.
  2.  
  3. Remove the air cleaner assembly.
  4.  
  5. Inspect the L-shaped tube from the throttle body to the MAP for cracks, blockage, and damage. Repair as necessary.
  6.  
  7. Unplug the MAP sensor connector.
  8.  
  9. Test the MAP sensor output voltage at the MAP sensor connector between terminals A and B. With ignition
  10.  
  11. ON and the engine OFF, the voltage should be between 4-5 volts. If no voltage is present, proceed to Step 8.
  12.  
  13. Test MAP sensor supply voltage at sensor connector between terminals A and C with the ignition ON and engine off, voltage should be 4.5-5.0 volts. If no voltage is present, proceed to Step 8.
  14.  
  15. Test the MAP sensor ground circuit at terminal A of the MAP connector; voltage should be less than 0.2 volts. If not inspect for open harness from pin 4 of ECM harness and terminal A. If no voltage is present, proceed to the next step.
  16.  
  17. Turn the ignition OFF.
  18.  
  19. Disconnect the ECM harness from the ECM.
  20.  
  21. Test the MAP sensor output voltage at the ECM connector. At the ECM harness connector test pin 1 of the connector, the voltage should be the same as at the MAP sensor in Step 5.
  22.  
  23. Check ECM harness connector pin 6 for the same voltage as in Step 6.
  24.  
  25. If all of the above tests pass, plug in ECM wiring harness and MAP sensor connector.
  26.  
  27. With the ignition in the ON position, and the engine OFF, remove the tube from the throttle body to the MAP sensor.
  28.  
  29. Connect a vacuum pump to the nipple on the MAP sensor, and pump the sensor to 20-27 in. Hg. of vacuum. Check the sensor output voltage, it should be below 1.8 volts. If not, replace the MAP sensor. If the voltage is OK, proceed to next step.
  30.  
  31. Relieve vacuum pressure on the sensor, and then check the output voltage. The voltage should be 4-5 volts; if not, replace the MAP sensor.
  32.  
  33. Install the air cleaner assembly.
  34.  
  35. Install the engine cover.

    Click image to see an enlarged view

    Fig.



    Click image to see an enlarged view

    Fig.

  36.  


WARNING
Testing the wiring harness with the ECM still connected can cause serious damage to the processor. ALWAYS disconnect the ECM before testing the wiring harness, unless instructed otherwise.

  1. Remove the engine cover.
  2.  
  3. Remove the air cleaner assembly.
  4.  
  5. Inspect the L-shaped tube from the throttle body to the MAP for cracks, blockage, and damage. Repair as necessary.
  6.  
  7. Unplug the MAP sensor connector.
  8.  
  9. Test the MAP sensor output voltage at the MAP sensor connector between terminals A and B. With ignition
  10.  
  11. ON and the engine OFF, the voltage should be between 4-5 volts. If no voltage is present, proceed to Step 8.
  12.  
  13. Test MAP sensor supply voltage at sensor connector between terminals A and C with the ignition ON and engine off, voltage should be 4.5-5.0 volts. If no voltage is present, proceed to Step 8.
  14.  
  15. Test the MAP sensor ground circuit at terminal A of the MAP connector; voltage should be less than 0.2 volts. If not inspect for open harness from pin 4 of ECM harness and terminal A. If no voltage is present, proceed to the next step.
  16.  
  17. Turn the ignition OFF.
  18.  
  19. Disconnect the ECM harness from the ECM.
  20.  
  21. Test the MAP sensor output voltage at the ECM connector. At the ECM harness connector test pin 1 of the connector, the voltage should be the same as at the MAP sensor in Step 5.
  22.  
  23. Check ECM harness connector pin 6 for the same voltage as in Step 6.
  24.  
  25. If all of the above tests pass, plug in ECM wiring harness and MAP sensor connector.
  26.  
  27. With the ignition in the ON position, and the engine OFF, remove the tube from the throttle body to the MAP sensor.
  28.  
  29. Connect a vacuum pump to the nipple on the MAP sensor, and pump the sensor to 20-27 in. Hg. of vacuum. Check the sensor output voltage, it should be below 1.8 volts. If not, replace the MAP sensor. If the voltage is OK, proceed to next step.
  30.  
  31. Relieve vacuum pressure on the sensor, and then check the output voltage. The voltage should be 4-5 volts; if not, replace the MAP sensor.
  32.  
  33. Install the air cleaner assembly.
  34.  
  35. Install the engine cover.

    Click image to see an enlarged view

    Fig.



    Click image to see an enlarged view

    Fig.

  36.  

 
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