Nissan Sentra/Pulsar/NX 1982-1996 Repair Guide

Vacuum Sensor

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OPERATION



The vacuum sensor is part of the Spark Timing Control System. The sensor provides an engine load signal to the ECM. The sensor converts manifold vacuum into an electrical signal, which is transmitted to the ECM. The ECM uses this signal, along with coolant temperature and engine speed inputs, to optimize the ignition timing.

TESTING



1984-88 Federal and 1987-88 California Models

See Figure 1



Click image to see an enlarged view

Fig. Fig. 1: Disconnect the vacuum hose from the sensor and connect a vacuum pump as shown

  1. Disconnect ECC 20 pin connector from control unit.
  2.  
  3. Connect a voltmeter between ECC control unit harness terminal 9 and a known good engine ground.
  4.  
  5. Disconnect vacuum hose for vacuum sensor and connect vacuum pump to vacuum sensor.
  6.  
  7. With no vacuum applied to the sensor, the voltmeter should read approximately 4.0 volts.

    If the reading was within specifications, proceed to the next step.
     
    If the reading was not within specifications, check power supply and wiring to sensor. If okay, replace the sensor and retest.
     

  8.  
  9. Using the vacuum pump, apply 25.0 in.Hg to the sensor. The voltage measurement should be approximately 0.5 volts.

    If the reading was within specifications, the sensor is okay.
     
    If the reading was not within specifications, replace the sensor and retest.
     

  10.  

REMOVAL & INSTALLATION



  1. Disconnect the vacuum hose from the sensor.
  2.  
  3. Disconnect the electrical connector from the sensor.
  4.  
  5. Remove the two bolt securing the sensor to the firewall.
  6.  
  7. Installation is the reverse of the removal procedure.
  8.  

 
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