Malibu, Malibu MAXX 2006-2008

Manifold Absolute Pressure Sensor

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Operation



The Manifold Absolute Pressure (MAP) sensor measures the pressure inside the intake manifold. Pressure in the intake manifold is affected by engine speed, throttle opening, air temperature, and Barometric Pressure (BARO). A diaphragm within the MAP sensor is displaced by the pressure changes that occur from the varying load and operating conditions of the engine. The sensor translates this action into electrical resistance. The MAP sensor wiring includes 3 circuits. The engine control module (ECM) supplies a regulated 5 volts to the sensor on a 5-volt reference circuit. The ECM supplies a ground on a low reference circuit. The MAP sensor provides a signal voltage to the ECM, relative to the pressure changes, on the MAP sensor signal circuit. The ECM converts the signal voltage input to a pressure value.

Under normal operation the greatest pressure that can exist in the intake manifold is equal to BARO. This occurs when the vehicle is operated at Wide-Open Throttle (WOT) or when the ignition is on while the engine is off. Under these conditions, the ECM uses the MAP sensor to determine the current BARO. The least manifold pressures occur when the vehicle is idling or decelerating. MAP can range from 10 kPa, when pressures are less, to as great as 104 kPa, depending on the current BARO. The ECM monitors the MAP sensor signal for pressure outside of the normal range.

Removal & Installation



2.2L (L61) Engine
  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Remove the throttle body.
  4.  
  5. Disconnect the engine wiring harness electrical connector from the Manifold Absolute Pressure (MAP) sensor.
  6.  
  7. Remove the MAP sensor and the MAP sensor port seal if it is still retained in the intake manifold.
  8.  

To install:

  1. Install the MAP sensor with the port seal into the intake manifold.
  2.  
  3. Connect the engine wiring harness electrical connector to the MAP sensor.
  4.  
  5. Install the throttle body.
  6.  

3.5L (LZ4) Engine
  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Remove the intake manifold cover.
  4.  
  5. Disconnect the engine wiring harness electrical connector from the Manifold Absolute Pressure (MAP) sensor.
  6.  
  7. Remove the spark plug wire clip from the MAP sensor bracket, if necessary.
  8.  
  9. Remove the upper intake manifold bolt.
  10.  
  11. Remove the MAP sensor bracket.
  12.  
  13. Remove the MAP sensor and seal from the upper intake manifold. Discard the seal.
  14.  

To install:

  1. Lubricate the new MAP sensor seal with clean engine oil.
  2.  
  3. Install the MAP sensor into the upper intake manifold.
  4.  
  5. Place the MAP sensor bracket into position.
  6.  
  7. Install the upper intake manifold bolt and tighten to 18 ft. lbs. (25 Nm).
  8.  
  9. Install the spark plug wire clip to the MAP sensor bracket, if necessary.
  10.  
  11. Connect the engine wiring harness electrical connector to the MAP sensor.
  12.  
  13. Install the intake manifold cover.
  14.  

3.9L (LZ9) Engine
  1. Before servicing the vehicle, refer to the Precautions Section.
  2.  
  3. Remove the intake manifold cover.
  4.  
  5. Disconnect the Manifold Absolute Pressure (MAP) sensor electrical connector.
  6.  
  7. Remove the spark plug wire clip from the intake manifold bracket, if necessary.
  8.  
  9. Remove the MAP sensor bolt.
  10.  
  11. Remove the MAP sensor.
  12.  
  13. Remove the MAP sensor seal from the upper intake manifold.
  14.  

To install:

  1. Install the MAP sensor seal into the upper intake manifold.
  2.  
  3. Install the MAP sensor.
  4.  
  5. Install the MAP sensor bolt and tighten to 89 inch. lbs. (10 Nm).
  6.  
  7. If required, install the spark plug wire clip to the intake manifold bracket.
  8.  
  9. Connect the MAP sensor electrical connector.
  10.  
  11. Install the intake manifold cover.
  12.  

Testing



Check the Manifold Absolute Pressure (MAP) sensor circuit as follows:

  1. Ignition OFF, disconnect the MAP harness connector at the MAP sensor.
  2.  
  3. Ignition OFF, test for less than 5 ohms of resistance between the low reference circuit terminal 2 and ground.
  4.  
  5. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  6.  
  7. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 1 and ground.
  8.  
  9. If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
  10.  
  11. If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  12.  
  13. Verify the scan tool MAP Sensor parameter is less than 1 kPa.
  14.  
  15. If greater than the specified range, test the signal circuit terminal 3 for a short to voltage. If the circuit tests normal, replace the ECM.
  16.  
  17. Install a 3A fused jumper wire between the signal circuit terminal 3 and the 5-volt reference circuit terminal 1. Verify the scan tool MAP Sensor parameter is greater than 126 kPa.
  18.  
  19. If less than the specified range, test the signal circuit terminal 3 for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
  20.  
  21. If all circuits test normal, test or replace the MAP sensor.

    Click image to see an enlarged view

    Fig. Manifold Absolute Pressure (MAP) sensor electrical connector

  22.  

Check the Manifold Absolute Pressure (MAP) sensor as follows:

  1. Turn ON the ignition, with the engine OFF, and remove the MAP sensor.
  2.  
  3. Install a 3A fused jumper wire between the 5-volt reference circuit terminal 1 and the corresponding terminal of the MAP sensor.
  4.  
  5. Install a jumper wire between the low reference circuit terminal 2 of the MAP sensor and ground.
  6.  
  7. Install a jumper wire at terminal 3 of the MAP sensor.
  8.  
  9. Connect a Digital Multi-Meter (DMM) between the jumper wire from terminal 3 of the MAP sensor and ground.
  10.  
  11. Install the J 35555 Vacuum tester to the MAP sensor vacuum port. Slowly apply vacuum to the sensor while observing the voltage on the DMM. The voltage should vary between 0-5.2 volts, without any spikes or dropouts
  12.  
  13. If the voltage is not within the specified range or is erratic, replace the MAP sensor.
  14.  

 
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