Chrysler Front Wheel Drive Cars 4-CYL 1981-1995 Repair Information

Manifold Absolute Pressure (MAP) Sensor

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OPERATION



Chrysler Electronic Fuel Injection (EFI) and Multi-Point Fuel Injection (MFI) Systems

See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: The MAP sensor is mounted on the fire wall in the engine compartment

The MFI system is used on 2.2L and 2.5L turbocharged and flex fuel engines.

The manifold absolute pressure (MAP) sensor is a device which monitors manifold vacuum. It is connected to a vacuum nipple on the throttle body and electrically to the engine controller. The sensor transmits manifold vacuum conditions and barometric pressure changes to the engine controller. The MAP sensor data is used along with data from other sensors to determine the correct air/fuel mixture.

Eagle Throttle Body Fuel Injection (TBI) System

The Eagle TBI system is used only on 2.5L Premier engines.

The Manifold Absolute Pressure (MAP) sensor is mounted under the hood on the fire wall and is connected to the throttle body with a vacuum line. The MAP sensor reacts to pressure changes in the intake manifold, and sends this information the PCM. As engine load changes, the intake manifold pressure varies, causing the MAP sensors resistance to change. The change in the MAP sensor resistance results in a different input voltage to the PCM. The the MAP sensor also supplies the PCM with information relating to ambient barometric pressure during engine start-up (cranking) and to engine load while the engine is running. The PCM computes the signal received from the MAP sensor and adjusts the air/fuel mixture accordingly.

TESTING



Chrysler Electronic Fuel Injection (EFI) and Multi-Point Fuel Injection (MFI) Systems

This test should be performed with the engine cold (room temperature).

  1. Backprobe the dark green/red tracer wire from the MAP sensor connector with a voltmeter (do not unplug the MAP connector).
  2.  

A Diagnostic Read-out Box (DRB or DRB-II) can also be used to measure the voltage of the MAP sensor. For more information, refer to the scan tool's manufacturer's instructions.

  1. If a DRB scan tool is being used, set it up as follows:
    1. Connect Chrysler DRB II or an equivalent scan tool to the diagnostic connector.
    2.  
    3. Place the scan tool into Sensor Test Mode number 8 .
    4.  

  2.  
  3. Disconnect the vacuum hose from the map sensor and connect a hand-held vacuum pump to the sensor vacuum port.
  4.  
  5. Turn the ignition key ON , but do not start the engine.
  6.  
  7. Apply 5 in. Hg (17 kPa) of vacuum to the sensor and record the reading on the voltmeter/scan tool.
  8.  
  9. While observing the voltmeter/scan tool, continue to slowly apply vacuum to the sensor until 20 in. Hg. (68 kPa) is reached. The voltage should decrease smoothly without any interruptions.

    If the sensor does not perform as specified, replace the sensor and retest
     
    If the sensor performs as specified proceed to the next step
     

  10.  
  11. Record the voltmeter/scan tool reading with 20 in. Hg (67.5 kPa) of vacuum applied to the sensor. Subtract the second reading from the first reading (i.e. reading at 5 in. Hg.-reading at 20 in. Hg=difference).

    If the difference is between 2.3-2.9 volts, the sensor is okay. Check the wiring and vacuum supply to the sensor.
     
    If the difference is not between 2.3-2.9 volts, replace the sensor with a new one, then retest.
     

  12.  

Eagle Throttle Body Fuel Injection (TBI) System

See Figure 2

Click image to see an enlarged view

Fig. Fig. 2: Manifold Absolute Pressure (MAP) sensor terminal identification

When testing the sensor, use a high input impedance digital volt-ohmmeter. Insert the tester leads through the back of the connector. Do not disconnect the electrical harness.

  1. Inspect the vacuum hose connections at the at the sensor and throttle body. Repair if necessary.
  2.  

For the following step, do not unplug the sensor connector; it must stay plugged in.

  1. Check the MAP sensor output voltage by inserting the negative lead of the voltmeter into the back of terminal A and the positive test leads through the back of the harness connector terminal B (as marked on the sensor body). With the ignition switch in the ON position and the engine OFF , the output voltage should be 4-5 volts.
  2.  
  3. Start the engine and allow the idle to stabilize at normal operating temperature. The output voltage should drop to 1.5-2.1 volts.
  4.  
  5. Test the PCM terminal C6 for the same voltage described above to verify the wire harness condition. Repair if necessary.
  6.  
  7. Test the MAP sensor supply voltage at the sensor connection terminal C with the ignition ON . The voltage should be 5 volts. Check the supply voltage at terminal C14 of the PCM. This should also be 5 volts.
  8.  
  9. Using an ohmmeter, test the MAP sensor ground circuit at the sensor connection terminal A and at the PCM terminal D3 . Repair the wiring harness if necessary.
  10.  

REMOVAL & INSTALLATION

Chrysler Electronic Fuel Injection (EFI), Multi-point Fuel Injection (MFI) and Eagle Throttle Body Fuel Injection (TBI) Systems

  1. Disconnect the negative battery cable.
  2.  
  3. Unplug the electrical connector from the sensor.
  4.  
  5. If so equipped, disconnect the vacuum hose from the sensor.
  6.  
  7. Remove the MAP sensor mounting fasteners.
  8.  
  9. Remove the sensor from the vehicle.
  10.  

To install:
  1. Install the MAP sensor into its position and secure in place with the mounting screws. Tighten the screws until snug.
  2.  
  3. Connect the vacuum hose, if so equipped.
  4.  
  5. Plug the electrical connector back into the sensor. Make certain that the connector is clean and snug fitting.
  6.  
  7. Connect the battery cable.
  8.  

 
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