Volkswagen Cars 2000-05

Manifold Absolute Pressure Sensor

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Operation



The amount of fuel sent to the injectors is affected, in part, by the signals to the ECM from the altitude compensator. As altitude increases (decreasing air pressure) the fuel mixture will be adjusted accordingly. The altitude compensator continuously adapts the injected fuel quantity to the changing air pressure.

Removal & Installation



  1. Turn the ignition switch to the OFF position.
  2.  
  3. Disconnect the Manifold Absolute Pressure sensor harness electrical connector.
  4.  
  5. Using a suitable tool, remove Manifold Absolute Pressure sensor.
  6.  
  7. Installation is in reverse order of removal.
  8.  

Testing



1.9L Turbo Diesel

NOTE
The altitude or Barometric pressure sensor is located in the diesel direct injection system ECM. The Manifold Absolute Pressure (MAP) sensor is a separate component and is located together with the Intake Air Temperature sensor in a housing on the air intake pipe.

  1. Connect a VAG 1551/1552 scan tool.
  2.  
  3. Switch the ignition 'ON', but Do NOT start the engine.
  4.  
  5. Press '0' and '1' buttons to select address word 01 'Engine Electronics.'
  6.  
  7. Press '0' and '8' buttons to select Function 08 'Read Measuring Value Block.'
  8.  
  9. Press 'Q' button to enter input.
  10.  
  11. Press '0', '1' and '0' buttons to select display group number '10'.
  12.  
  13. Press 'Q' button to enter input; 'Display' will appear as shown in the illustration.
  14.  



Click image to see an enlarged view

Fig. Display will appear as shown (Passat 1.9L Turbo Diesel)

  1. Compare display zone '2' (BARO sensor F96) with display zone '3' (MAP sensor G71). The pressures must be close to the same, within a tolerance of 30 mbar.
  2.  

If specification not obtained, use the VAG 1397A turbocharger test tool to establish an independent reference value. Set the tool to test range '1' (absolute pressure). An accurately calibrated barometer can also be used.

  1. If value in display zone '3' deviates from the tolerance range, press button '0' and '6' to select 'Function 06: End Transfer.'
  2.  
  3. Press the 'Q' button to enter input.
  4.  
  5. Start the engine.
  6.  
  7. Press the '0' and '8' buttons to select 'Function 08': 'Read Measuring Value Block.'
  8.  
  9. Press the 'Q' button to enter input.
  10.  
  11. Press the '0', '1' and '0' buttons to select 'Display Group 10.'
  12.  
  13. Press the 'Q' button to enter input.
  14.  
  15. Disconnect the engine speed sensor harness connector.
  16.  
  17. Observe the value in display field '3' (MAP sensor).
  18.  
  19. The value must drop consistently and then equate to the BARO sensor displayed value (display field '2').
  20.  

If the proper specification is obtained, replace the MAP sensor assembly, which also includes the IAT sensor.

If the specification is not obtained, press button '0' and '6' to select 'Function 06: End transfer.'

  1. Press the 'Q' button to enter input.
  2.  
  3. Switch 'OFF' the ignition.
  4.  
  5. Connect a VAG 1598/22 Test Box to the ECM wiring harness.
  6.  
  7. Check wiring for open circuit between Test Box and harness connector using wiring diagram. Check at the following points:
  8.  


    Terminal 1 and socket 33
     
    Terminal 2 and socket 17
     

  9. At each test, the specification should show a maximum resistance 1.5 ohms.
  10.  
  11. Check the wires for shorts to one another, to vehicle ground, and to battery voltage (B+). There should be infinite ohms.
  12.  
  13. If the wiring is OK, replace the ECM-J248.
  14.  



Click image to see an enlarged view

Fig. The ECM 4-pin connector on the Passat 1.9L Turbo Diesel

 
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