Commander 2006-2007

Knock Sensor

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Operation



Two knock sensors are used; one for each cylinder bank. When the knock sensor detects a knock in one of the cylinders on the corresponding bank, it sends an input signal to the Powertrain Control Module (PCM). In response, the PCM retards ignition timing for all cylinders by a scheduled amount.

Knock sensors contain a piezoelectric material which constantly vibrates and sends an input voltage (signal) to the PCM while the engine operates. As the intensity of the crystal's vibration increases, the knock sensor output voltage also increases

Removal & Installation



3.7L & 4.7L Engines
  1. Disconnect the knock sensor dual pigtail harness from engine wiring harness. This connection is made near rear of engine.
  2.  
  3. Remove the intake manifold
  4.  
  5. Remove the Knock Sensor (KS) mounting bolts.
  6.  
  7. Remove the sensors from engine.

    Click image to see an enlarged view

    Fig. Disconnect the wiring harness (4) and remove the intake manifold (3) remove the knock sensors (1,2)-3.7L & 4.7L Engines

  8.  

To install:

  1. Thoroughly clean the KS mounting holes.
  2.  
  3. Install the sensors into the engine block. Tighten the mounting bolts to 15 ft. lbs. (20 Nm).
  4.  
  5. Install the intake manifold.
  6.  
  7. Connect the KS wiring harness to the engine wiring harness at the rear of the engine.
  8.  

5.7L Engine
  1. Raise and safely support the vehicle.
  2.  
  3. Disconnect the Knock Sensor (KS) electrical connector.
  4.  
  5. Remove the KS mounting bolt.
  6.  
  7. Remove the sensor from the engine.
  8.  

To install:

  1. Thoroughly clean the KS mounting holes.
  2.  
  3. Install the sensors into the engine block. Tighten the mounting bolts to 15 ft. lbs. (20 Nm).
  4.  
  5. Connect the KS electrical connectors.
  6.  
  7. Lower the vehicle.
  8.  

Testing



  1. Start the engine and allow it to reach normal operating temperature. Using a diagnostic scan tool, check for the presence of any Diagnostic Trouble Codes (DTCs). Record and address these codes as necessary.
  2.  
  3. Refer to any Technical Service Bulletins (TSBs) that may apply.
  4.  
  5. Review the scan tool Freeze Frame information. If possible, try to duplicate the conditions under which the DTC set.
  6.  
  7. With the engine running at normal operating temperature, monitor the scan tool parameters related to the DTC while wiggling the wire harness. Look for parameter values to change and/or a DTC to set. Turn the ignition off.
  8.  
  9. Visually inspect the related wire harness. Disconnect all the related harness connectors. Look for any chafed, pierced, pinched, partially broken wires and broken, bent, pushed out, or corroded terminals. Perform a voltage drop test on the related circuits between the suspected inoperative component and the PCM.
    CAUTION
    Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool no. 8815 to perform diagnosis.

  10.  
  11. Inspect and clean all PCM, engine, and chassis grounds that are related to the most current DTC.
  12.  
  13. If numerous trouble codes were set, use a wire schematic and look for any common ground or supply circuits.
  14.  
  15. For any Relay DTCs, actuate the Relay with the scan tool and wiggle the related wire harness to try to interrupt the actuation.
  16.  
  17. For intermittent Evaporative Emission trouble codes perform a visual and physical inspection of the related parts including hoses and the Fuel Filler cap.
  18.  
  19. Use the scan tool to perform a System Test if one applies to failing component. A co-pilot, data recorder, and/or lab scope should be used to help diagnose intermittent conditions.
  20.  

 
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