Corvette 1997-2005

Knock Sensor

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Operation



The knock sensor system enables the PCM to control ignition timing for best performance while protecting the engine from detonation.

The KS system uses one or 2 flat response 2-wire sensors. The sensor uses piezo-electric crystal technology that produces an AC voltage signal of varying amplitude and frequency based on the engine vibration or noise level. The control module receives the KS signal through a signal circuit. The KS ground is supplied by the control module through a low reference circuit. The control module learns a minimum noise level, or background noise, at idle from the KS and uses calibrated values for the rest of the RPM range.

In order to determine which cylinders are knocking, the control module only uses KS signal information when each cylinder is near Top Dead Center (TDC) of the firing stroke. If knock is present, the signal will range outside of the noise channel. If the control module has determined that knock is present, it will retard the ignition timing to attempt to eliminate the knock. The control module will always try to work back to a zero compensation level, or no spark retard.

Removal & Installation



  1. Raise and safely support the vehicle.
  2.  
  3. Remove the exhaust manifold.
  4.  
  5. Unplug the harness connection as shown (3) from the knock sensor.
  6.  
  7. Remove the bolt (1) securing the sensor, then remove the knock sensor (2) from the engine.
  8.  
  9. Installation is the reverse of removal. Tighten the bolt to 15 ft. lbs. (20 Nm).

    Click image to see an enlarged view

    Fig. Knock sensor mounting-left side



    Click image to see an enlarged view

    Fig. Knock sensor mounting-right side

  10.  

5.7L Engine
  1. Remove the intake manifold.
  2.  
  3. Remove the knock sensor wiring harness assembly.
  4.  
  5. Remove the knock sensor.
  6.  
  7. Installation is the reverse of the removal procedure. Tighten the knock sensor to 20 Nm (15 ft. lbs.).
  8.  

6.0L V8
  1. Disconnect the negative battery cable.
  2.  
  3. Remove the left exhaust manifold.
  4.  
  5. Remove the left catalytic converter.
  6.  
  7. On right side, remove starter.
  8.  
  9. Remove the mounting bolt for the knock sensor 1.
  10.  
  11. Disconnect the electrical connector of the knock sensor from the engine harness. Remove the knock sensor from the engine block.
  12.  

To install:

  1. Reconnect the engine harness and the knock sensor electrical connectors.
  2.  
  3. Position the knock sensor 2 on the engine block.
  4.  
  5. Install the mounting bolt for the knock sensor 2.
  6.  
  7. Tighten the knock sensor mounting bolt (1). Tighten the knock sensor mounting bolt to 20 Nm (15 ft. lbs.).
  8.  
  9. On right side, install starter.
  10.  
  11. Install the left catalytic converter.
  12.  
  13. Install the left exhaust manifold.
  14.  
  15. Connect the negative battery cable.
  16.  
  17. Program the transmitters.
  18.  

Testing



  1. Connect a digital multimeter to the KS signal circuit and to the KS low reference circuit at the KS.
  2.  
  3. Set the multimeter to the 400 mv AC hertz scale and wait for the display to stabilize at 0 Hz.
  4.  
  5. Tap on the engine block with a non-metallic object near the KS while observing the signal indicated on the multimeter.
    NOTE
    Do not tap on plastic engine components.

  6.  
  7. The multimeter should display a fluctuating frequency while tapping on the engine block. If not, replace the sensor.
  8.  

 
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