ParkAvenue 1997-1999

Manifold Absolute Pressure Sensor

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Operation



Specific to:

Buick LeSabre 1986-1999

Buick Park Avenue 1996-1999

Oldsmobile 88 1992-1999

Oldsmobile Delta 88 1986-1988

Oldsmobile LSS 1996-1999

Pontiac Bonneville 1987-1999

The Manifold Absolute Pressure (MAP) sensor, used on 1996-99 vehicles, measures the changes in intake manifold pressure which result from engine load/speed changes, and converts this information to a voltage output. The MAP sensor reading is the opposite of a vacuum gauge reading: when manifold pressure is high, MAP sensor value is high and vacuum is low. A MAP sensor will produce a low output on engine coast-down with a closed throttle while a wide open throttle will produce a high output. The high output is produced because the pressure inside the manifold is the same as outside the manifold, so 100 percent of the outside air pressure is measured.

The MAP sensor is also used to measure barometric pressure under certain conditions, which allows the PCM to automatically adjust for different altitudes.

The MAP sensor changes the 5 volt signal supplied by the PCM, which reads the change and uses the information to control fuel delivery and ignition timing.

Removal & Installation



3.8L Engine
VIN 1 Engine

Specific to:

Buick LeSabre 1986-1999

Buick Park Avenue 1996-1999

Oldsmobile 88 1992-1999

Oldsmobile Delta 88 1986-1988

Oldsmobile LSS 1996-1999

Pontiac Bonneville 1987-1999

  1. Disconnect the negative battery cable.
  2.  
  3. Unfasten the two retaining screws.
  4.  
  5. Detach the electrical connector and vacuum hose from the MAP sensor.
  6.  
  7. Remove the MAP sensor from the bracket.
  8.  



Click image to see an enlarged view

Fig. Exploded view of the MAP sensor mounting - 3.8L (VIN 1) engine

To install:

  1. Attach the vacuum hose and electrical connector to the MAP sensor.
  2.  
  3. Position the MAP sensor to the bracket, then secure with the two retaining screws.
  4.  
  5. Connect the negative battery cable.
  6.  

VIN K Engine

Specific to:

Buick LeSabre 1986-1999

Buick Park Avenue 1996-1999

Oldsmobile 88 1992-1999

Oldsmobile Delta 88 1986-1988

Oldsmobile LSS 1996-1999

Pontiac Bonneville 1987-1999

On these engines, the MAP sensor is mounted to the PCV valve cover.

  1. Disconnect the negative battery cable.
  2.  
  3. Detach the MAP sensor electrical connector.
  4.  
  5. Carefully bend the locking tabs holding the MAP sensor to the PCV valve cover, just enough to remove the MAP sensor.
  6.  
  7. Pull the MAP sensor straight out of the PCV valve cover.
  8.  



Click image to see an enlarged view

Fig. On the 3.8L (VIN K) engine, the MAP sensor (1) is mounted in the PCV valve cover (2)

To install:

  1. Make sure that the seal is installed on the MAP sensor and that it is not damaged.
  2.  
  3. Position and install the MAP sensor to the PCV valve cover. Make sure the locking tabs engage to hold the sensor to the cover.
  4.  
  5. Attach the sensor electrical connector.
  6.  
  7. Connect the negative battery cable.
  8.  

Testing



Specific to:

Buick LeSabre 1986-1999

Buick Park Avenue 1996-1999

Oldsmobile 88 1992-1999

Oldsmobile Delta 88 1986-1988

Oldsmobile LSS 1996-1999

Pontiac Bonneville 1987-1999

  1. Visually check the connector, making sure it is properly connected and that all of its terminals are straight, tight and free of corrosion.
  2.  
  3. With the ignition ON , check the voltage between terminals A and B. It should be above 4 volts. Apply 15 in. Hg of vacuum at the MAP vacuum port and check the voltage again. The voltage should be 2 volts now.
  4.  



Click image to see an enlarged view

Fig. Manifold Absolute Pressure (MAP) sensor circuit

When pumping up and releasing the vacuum, check to make sure the voltage readings are smooth. When applying vacuum to the sensor, the change in voltage should happen instantly. A slow change in voltage could point to a faulty sensor.



Click image to see an enlarged view

Fig. MAP sensor voltage specifications

  1. If the sensor voltage is not within specification, check for a 5 volt reference at terminal C. If the reference signal is found, the sensor is faulty.
  2.  
  3. If the sensor and circuits are functional, the PCM may be faulty.
  4.  

 
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