Chrysler Full-Size Vans 1989-1998 Repair Guide

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.

TESTING



See Figures 1, 2 and 3

  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.  

ON

and the engine OFF , the voltage should be between 4-5 volts. If no voltage is present, proceed to Step 8.

  1. 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.
  2.  
  3. 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.
  4.  
  5. Turn the ignition OFF .
  6.  
  7. Disconnect the ECM harness from the ECM.
  8.  


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. 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.
  2.  
  3. Check ECM harness connector pin 6 for the same voltage as in Step 6.
  4.  
  5. If all of the above tests pass, plug in ECM wiring harness and MAP sensor connector.
  6.  
  7. With the ignition in the ON position, and the engine OFF , remove the tube from the throttle body to the MAP sensor.
  8.  
  9. 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.
  10.  
  11. Relieve vacuum pressure on the sensor, then check the output voltage. The voltage should be 4-5 volts; if not, replace the MAP sensor.
  12.  
  13. Install the air cleaner assembly.
  14.  
  15. Install the engine cover.
  16.  



Click image to see an enlarged view

Fig. Fig. 1: Use a voltmeter to check the MAP sensor for signal



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Fig. Fig. 2: The MAP sensor's electrical connector terminal identification-MFI vehicles



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Fig. Fig. 3: The MAP sensor circuit schematic for MFI equipped vehicles

REMOVAL & INSTALLATION



See Figure 4

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the engine cover.
  4.  
  5. Remove the air cleaner assembly.
  6.  

On some models it may be necessary to remove the throttle body from the vehicle to access the MAP sensor bolts. If applicable, refer to the procedure in Fuel System .

  1. Remove the two MAP sensor retaining bolts.
  2.  
  3. Slide the L-shaped tube to the MAP sensor from the throttle body off while removing the MAP sensor from the throttle body.
  4.  

To install:
  1. Install the L-shaped tube onto the MAP sensor.
  2.  
  3. Install the MAP sensor onto the throttle body assembly. Tighten the retaining bolts to 25 inch lbs. (3 Nm). If applicable, install the throttle body.
  4.  
  5. Install the air cleaner assembly.
  6.  
  7. Install the engine cover.
  8.  
  9. Connect the negative battery cable.
  10.  



Click image to see an enlarged view

Fig. Fig. 4: The MAP sensor location for TBI equipped vehicles

 
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