Mitsubishi Eclipse 1990-1998 Repair Guide

Knock Sensor

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OPERATION



The knock sensor is normally mounted to the rear side of the engine block. It reacts to the ping or knock caused during detonation by sending a signal to the ECU. The ECU retards the timing to eliminate the detonation.

If the knock sensor is experiencing functional problems, a slight reduction in engine power may be felt. This is because the ignition timing will be forcibly retarded.

TESTING



See Figures 1 and 2

The knock sensor test requires the use of an oscilloscope.

  1. Position test probe of oscilloscope lead to the oscilloscope pick-up point as shown in the illustration.
  2.  
  3. Start the engine and allow to idle. Accelerate the engine to a maximum speed of 5,000 rpm and check the waveform on the scope.
  4.  



Click image to see an enlarged view

Fig. Fig. 1: Knock sensor circuit. Note positioning of oscilloscope during testing.



Click image to see an enlarged view

Fig. Fig. 2: Ideal test pattern of knock sensor as seen on an oscilloscope

  1. If the test pattern obtained differentiates from the desired pattern shown in the illustration, replace the knock sensor.
  2.  

REMOVAL & INSTALLATION



See Figures 3 and 4

  1. Disconnect the negative battery cable.
  2.  
  3. For 2.0L non-turbo engines, remove the engine under cover.
  4.  



Click image to see an enlarged view

Fig. Fig. 3: Exploded view of the knock sensor mounting-1997 2.0L non-turbo engine shown

  1. Detach the electrical connector at the sensor.
  2.  
  3. For 2.0L turbo engines, remove the intake manifold stay.
  4.  



Click image to see an enlarged view

Fig. Fig. 4: Exploded view of the knock sensor-1995-98 2.0L turbo engines

  1. Remove the sensor from the engine block.
  2.  

To install:
  1. Install the knock sensor in the opening in the engine block and tighten the sensor retainer.
  2.  
  3. Attach the electrical connector to the sensor.
  4.  
  5. Connect the negative battery cable.
  6.  

 
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