Chrysler Caravan/Voyager/Town and Country 1996-1999

Knock Sensor

Print

All engines covered in this guide, except the 3.0L engine, utilize a knock sensor.

OPERATION



See Figures 1 and 2



Click image to see an enlarged view

Fig. Fig. 1: Knock sensor location on the 2.4L engine



Click image to see an enlarged view

Fig. Fig. 2: Knock sensor location on the 3.3L and 3.8L engines

The knock sensor is threaded into the side of the cylinder block, in front of the starter. When the knock sensor detects a knock in one of the cylinders, it sends an input signal to the PCM. In response, the PCM retards ignition timing for all cylinders by a specific amount.

Knock sensors contain a piezoelectric material which sends an input signal (voltage) to the PCM. As the intensity of the engine knock vibration increases, the knock sensor output voltage also increases.

TESTING



See Figure 3



Click image to see an enlarged view

Fig. Fig. 3: Knock sensor schematic

Visually check the connector, making sure it is attached properly and that all of the terminals are straight, tight and free of corrosion.

A number of factors affect the engine knock sensor. A few of these are: ignition timing, cylinder pressure, fuel octane, etc. The knock sensor produces an AC voltage whose amplitude increases with the amount of engine knock. The knock sensor can be tested with a digital voltmeter. The knock sensor output voltage should measure between 80mV and 4 volts with the engine running between 576 and 2208 rpm. If the output falls outside of this range, a Diagnostic Trouble Code (DTC) will set.

REMOVAL & INSTALLATION



See Figures 1 and 2

The knock sensor is threaded into the side of the cylinder block, in front of the starter.

  1. Disconnect the negative battery cable.
  2.  
  3. Unplug the electrical connector from the knock sensor.
  4.  
  5. Use a crow's foot wrench to remove the knock sensor from the vehicle.
  6.  

To install:
  1. Install the sensor in the vehicle and tighten to 7 ft. lbs. (10 Nm). Make sure not to over or under-tighten the sensor, as is could adversely affect knock sensor performance, causing improper spark control.
  2.  
  3. Attach the knock sensor electrical connector.
  4.  
  5. Connect the negative battery cable.
  6.  

 
label.common.footer.alt.autozoneLogo