Vibe 2003-2005

Knock Sensor

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Operation



The KS is non-resonant design that is constructed of a piezoelectric element which generates an AC signal when vibrated. Normal engine operation will cause the KS to generate signals of known frequencies. When engine knock is present, the KS frequency changes. This signals the powertrain control module (PCM) to retard ignition timing. The PCM sends a bias voltage of 5 volts to the KS on the KS Signal High circuit. The PCM expects approximately 2.5 volts back on the KS Signal Low circuit. The KS generated AC signal rides on top of the bias voltage provided by the PCM.

Removal & Installation



  1. Remove the starter.
  2.  
  3. Disconnect the Knock Sensor (KS) harness connector.
  4.  
  5. Remove the KS retaining bolt.
  6.  
  7. Remove the KS.
  8.  

To install:

  1. Installation is the reverse of removal.
  2.  

Testing



  1. Turn OFF the ignition.
  2.  
  3. Disconnect the Knock Sensor (KS) electrical connector.
  4.  
  5. Turn ON the ignition, with the engine OFF.
  6.  
  7. Measure the voltage across the KS connector, harness side. The voltage should be 5 volts.
  8.  
  9. Measure the voltage from the KS Signal High circuit to a good ground. . The voltage should be 5 volts. If the voltage is less, check for an open in the signal low circuit. If the voltage is greater than 5 volts, check for an open or short in the signal high circuit.
  10.  
  11. Turn OFF the ignition.
  12.  
  13. Connect the KS electrical connector.
  14.  
  15. Disconnect the powertrain control module (PCM) electrical connector C2.
  16.  
  17. Measure the resistance between the KS Signal High circuit and the KS Signal Low circuit. The resistance should be 200 KOhms at 68 degrees F (20 degrees C). if not, check the sensor connections.
  18.  
  19. If there are no issues with the wiring and connectors, replace the sensor.

    Click image to see an enlarged view

    Fig. Knock (KS) sensor terminals; (1) Knock sensor signal low, (2) Knock sensor signal high

  20.  

 
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