Nissan 240SX/Altima 1993-1998 Repair Guide

Absolute Pressure Sensor

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OPERATION



The absolute pressure sensor is connected to the MAP/BARO switch solenoid valve by a hose. The sensor detects ambient barometric pressure and intake manifold pressure, and sends a voltage signal to the ECM. As pressure increases, the voltage rises. The absolute pressure sensor is not used to control the engine system. It is only used for on-board diagnosis.

TESTING



See Figure 1



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Fig. Fig. 1: Use a voltmeter to backprobe the absolute pressure sensor's center terminal. Repeat the test with vacuum applied

  1. Remove the absolute pressure sensor with its electrical harness connected.
  2.  
  3. Disconnect the vacuum hose from the sensor.
  4.  
  5. Turn the ignition switch ON .
  6.  
  7. Backprobe the sensor connector and check output voltage, as illustrated.
  8.  
  9. The voltage should be 3.2-4.8 volts.
  10.  
  11. Connect a hand powered vacuum pump and apply a vacuum of 7.87 in. Hg (26.7 kPa).
  12.  
  13. Voltage should be 1.0-1.4 volts lower than the value in Step 5.
  14.  
  15. If voltage is not within specification or does not respond as specified, check the power and ground circuits.
  16.  
  17. If the power and ground circuits are okay, the sensor may be faulty.
  18.  

REMOVAL & INSTALLATION



The absolute pressure sensor is mounted to the right strut tower in the engine compartment.

  1. Label and disconnect the electrical harness from the sensor.
  2.  
  3. Label and disconnect the vacuum hose from the sensor.
  4.  
  5. Remove the sensor mounting screws.
  6.  
  7. Remove the sensor from the strut tower.
  8.  

To install:
  1. Install the sensor on the strut tower and tighten the screws securely.
  2.  
  3. Connect the vacuum hose to the sensor.
  4.  
  5. Connect the electrical harness to the sensor.
  6.  

 
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