GM Grand Am/Achieva/Calais/Skylark/Somerset 1985-98

Knock Sensor (KS)

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OPERATION



The Knock Sensor (KS) detects abnormal vibration (spark knocking) in the engine. The sensor is mounted in the engine block near the cylinders. The sensor produces an AC output voltage which increases with the severity of the knock. This signal voltage inputs to the ECM/PCM. The computer control module then adjusts the timing to reduce the knock. This allows the engine to use maximum spark advance to improve driveability and fuel economy.

TESTING



There is no realistic way to test the operation of this sensor, since it only produces a signal when the engine is detonating. The sensor can be monitored with some scan tools by using a data display or other data stream information. Follow the instructions included with the scan tool for information on accessing the data.

REMOVAL & INSTALLATION



See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: The Knock Sensor (KS) is mounted in the engine block near the cylinders

  1. Disconnect the negative battery cable.
  2.  
  3. Raise and safely support the vehicle.
  4.  
  5. Detach the wiring harness connector from the Knock Sensor (KS).
  6.  
  7. Remove the knock sensor from the engine block.
  8.  

To install:
  1. Install the knock sensor into the engine block. Tighten to 14 ft. lbs. (19 Nm).
  2.  
  3. Attach the wiring harness connector to the sensor.
  4.  
  5. Carefully lower the vehicle.
  6.  
  7. Connect the negative battery cable.
  8.  

 
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