GM Cadillac Deville_Fleetwood_ELD_Seville 1990-1998

Mass Airflow Sensor

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OPERATION



The Mass Air Flow (MAF) sensor measures the amount of air that is ingested by the engine. Direct measurement of air entering the engine is more accurate than calculating airflow from other sensor inputs. The MAF sensor has a switched battery feed, a ground, a signal circuit and a signal return circuit.

The MAF sensor used on this vehicle is a hot film type and is used to measure airflow rate. The MAF output voltage is a function of the power required to keep the airflow sensing elements at a fixed temperature above airflow sensing elements at a fixed temperature above ambient temperature. Air flowing through the sensor cools the sensing elements. The amount of cooling is proportional to the amount of airflow. As airflow increases, a greater amount of current is required to maintain the hot film at a constant temperature. The MAF sensor converts the changes in current draw to a voltage signal read by the PCM. The PCM calculates airflow based on this signal.

TESTING



The scan tool reads the MAF value and displays it in grams per second (gm/s). Values should change rather quickly on acceleration, but values should remain stable at any given RPM. When the PCM detects a malfunction in the MAF sensor circuit, a DTC will set.

  1. Visually check the connector and make sure it is secure, clean, and tight.
  2.  
  3. Bring the engine to normal operating conditions, lightly tap on the MAF sensor (with a suitable tool), and wiggle the wires at the connector, watch for a change in the idle speed. A common problem is MAF sensor wire damage.
  4.  
  5. Backprobe the sensor connector using a DVOM set to the Hertz scale. Attach the leads to A and B while simulating driving conditions by blowing air across the wire in the sensor. There should be a frequency swing from air crossing the wire in the sensor. A normal flow signal will be close to 1200 Hertz. If the frequency does not register, or is not proportional to the airflow across the sensing wire, then the sensor is faulty.
  6.  
  7. Check for battery positive (source voltage) on terminal C and ground on terminal B. If voltage or ground do not register, check the circuits to the PCM for continuity.
  8.  
  9. If voltage checks are good at the electrical connector and a driveability problem still exists, it may be the MAF sensor.
  10.  
  11. If the sensor and circuits are functional, the PCM may be at fault.
  12.  

REMOVAL & INSTALLATION



3.0L Engine
  1. Disconnect the wiring harness from the MAF sensor, and the wiring harness from the IAT sensor.
  2.  
  3. Loosen the hose clamps from the air intake duct on either side of the IAT sensor.
  4.  
  5. Remove the air intake duct with the IAT sensor.
  6.  
  7. Loosen the hose clamp at the bottom of the MAF sensor.
  8.  
  9. Remove the MAF sensor from the lower air intake duct. Make a note of the installation position.
  10.  


NOTE
Do not disassemble the MAF sensor. Remove or install the sensor as a complete unit only. If there is external deformation of the grid, replace the MAF sensor.

To install:

  1. Installation is the reversal of the removal procedure.
  2.  



Click image to see an enlarged view

Fig. Location of the Mass Air Flow (MAF ) Sensor-3.0L engine

4.6L Engine
  1. Remove the intake air duct
  2.  
  3. Detach the MAF sensor electrical connector
  4.  
  5. Remove the 3 MAF sensor mounting screws and remove the sensor.
  6.  

To install:

  1. Installation is the reversal of the removal procedure.
  2.  

 
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