Toyota Previa 1991-1997 Repair Information

Knock Sensor

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To access the knock sensor, the engine and transmission must be removed from the vehicle.

OPERATION



The knock sensor is fitted into the cylinder block to detect engine knocking. This sensor contains a piezoelectric element which generates a voltage when it becomes deformed, which occurs when the cylinder block vibrates due to knocking. If the engine knocking occurs, ignition timing is retarded to suppress it.

TESTING



See Figure 1

  1. Remove the engine and transmission assembly from the vehicle
  2.  
  3. Remove the intake manifold.
  4.  
  5. Disconnect the wiring from the knock sensor.
  6.  
  7. Using tool 09816-30010 or an equivalent socket, remove the knock sensor from the vehicle.
  8.  
  9. Using an ohmmeter, check that there is no continuity between the terminal and the body.
  10.  



Click image to see an enlarged view

Fig. Fig. 1: Make sure there is no continuity between the body and terminal of the knock sensor

  1. If there is continuity, replace the sensor.
  2.  
  3. Install the knock sensor with the special tool, tighten securely to 33 ft. lbs. (44 Nm).
  4.  
  5. Connect the sensor wiring.
  6.  
  7. Install the intake manifold. Reinstall the engine in the vehicle.
  8.  

REMOVAL & INSTALLATION



  1. Remove the engine from the vehicle.
  2.  
  3. Remove the intake manifold.
  4.  
  5. Remove the knock sensor from the engine.
  6.  
  7. Inspect the vacuum hose over its entire length for any signs of cracking or splitting. The slightest leak can cause improper operation.
  8.  

To install:
  1. Install the knock sensor; tighten securely to 34 ft. lbs. (45 Nm).
  2.  
  3. Reinstall the intake manifold. Install the engine.
  4.  

 
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