Nissan 240SX/Altima 1993-1998 Repair Guide

Camshaft Position Sensor

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OPERATION



The Camshaft Position (CMP) sensor is a basic component of the engine control system. It monitors engine speed and piston position. These input signals to the ECM are used to control fuel injection, ignition timing and other functions.

The sensor has a rotor plate and a wave forming circuit. The rotor plate has 360 slits for a 1° signal and 4 slits for a 180° signal. The wave forming circuit consists of a Light Emitting Diode (LED) and photo diode.

The rotor plate is positioned between the LED and photo diode. The LED transmits light to generate rough shaped pulses. These pulses are converted into on/off signals by the wave forming circuit and sent to the ECM.

TESTING



See Figures 1 and 2



Click image to see an enlarged view

Fig. Fig. 1: Camshaft position sensor terminal locations-six-terminal connector



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Fig. Fig. 2: Camshaft position sensor terminal locations-four-terminal connector

  1. Remove the distributor assembly from the engine.
  2.  
  3. Disconnect the ignition wires and coil wire from the distributor.
  4.  

The camshaft position sensor electrical harness should remain connected.

  1. Turn the ignition switch ON .
  2.  
  3. Measure voltage between the camshaft position sensor terminals and ground, as illustrated.
  4.  
  5. With the engine's distributor shaft rotating slowly, voltage should fluctuate between 0 and 5 volts.
  6.  

If the voltage signal is checked with the engine running, the normal reading will be 2.3 volts (average voltage). An oscilloscope may also be used to view the pulse signal.

  1. If voltage does not fluctuate or is not within specification, check the circuits for damage.
  2.  
  3. If the circuits are functional, the sensor may be faulty.
  4.  
  5. Install the distributor and connect the ignition and coil wires.
  6.  
  7. Erase stored memory codes.
  8.  

REMOVAL & INSTALLATION



The camshaft position sensor is located inside the distributor. On some distributors, the camshaft position sensor is not serviceable (replacement parts may not be available separately). If the camshaft position sensor is serviceable, use the following procedure.

  1. Remove the distributor cap and wires.
  2.  
  3. Remove the rotor.
  4.  
  5. Remove the camshaft position sensor cap.
  6.  
  7. Remove the camshaft position sensor mounting screws.
  8.  
  9. Carefully remove the camshaft position sensor.
  10.  

To install:
  1. Position the camshaft position sensor in the distributor and tighten the mounting screws securely.
  2.  
  3. Install the camshaft position sensor cap.
  4.  
  5. Install the rotor.
  6.  
  7. Install the distributor cap and wires.
  8.  

 
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