Cherokee, Grand Cherokee, 1999-2005

Crankshaft Position Sensor

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Operation



3.7L V6

The Crankshaft Position (CKP) sensor is mounted into the right rear side of the cylinder block. It is positioned and bolted into a machined hole.

Engine speed and crankshaft position are provided through the CKP (Crankshaft Position) sensor. The sensor generates pulses that are the input sent to the Powertrain Control Module (PCM). The PCM interprets the sensor input to determine the crankshaft position. The PCM then uses this position, along with other inputs, to determine injector sequence and ignition timing.

Click image to see an enlarged view

Fig.

The sensor is a Hall effect device combined with an internal magnet. It is also sensitive to steel within a certain distance from it. A tone wheel (target wheel) is bolted to the engine crankshaft. This tone wheel has sets of notches at its outer edge. The notches cause a pulse to be generated when they pass under the sensor. The pulses are the input to the PCM.

Click image to see an enlarged view

Fig.

4.0L

The Crankshaft Position Sensor (CKP) is mounted to the transmission bellhousing at the left/rear side of the engine block. Engine speed and crankshaft position are provided through the crankshaft position sensor. The sensor generates pulses that are the input sent to the powertrain control module (PCM). The PCM interprets the sensor input to determine the crankshaft position. The PCM then uses this position, along with other inputs, to determine injector sequence and ignition timing. The sensor is a Hall effect device combined with an internal magnet. It is also sensitive to steel within a certain distance from it.

On 4.0L 6-cylinder engines, the flywheel/drive plate has 3 sets of four notches at its outer edge. The notches cause a pulse to be generated when they pass under the sensor. The pulses are the input to the PCM. For each engine revolution there are 3 sets of four pulses generated.

The trailing edge of the fourth notch, which causes the pulse, is four degrees before top dead center (TDC) of the corresponding piston. The engine will not operate if the PCM does not receive a crankshaft position sensor input.

Click image to see an enlarged view

Fig.



Click image to see an enlarged view

Fig.

4.7L

The Crankshaft Position Sensor (CKP) is mounted into the engine block above the starter motor. Engine speed and crankshaft position are provided through the crankshaft position sensor. The sensor generates pulses that are the input sent to the powertrain control module (PCM). The PCM interprets the sensor input to determine the crankshaft position. The PCM then uses this position, along with other inputs, to determine injector sequence and ignition timing. The sensor is a Hall effect device combined with an internal magnet. It is also sensitive to steel within a certain distance from it.

On the 4.7L V8 engine, a tone wheel is bolted to the engine crankshaft. This tone wheel has sets of notches at its outer edge. The notches cause a pulse to be generated when they pass under the sensor. The pulses are the input to the PCM.

Click image to see an enlarged view

Fig.



Click image to see an enlarged view

Fig.

5.7L V8 Engines

The crankshaft position sensor is located at the left rear of the engine just above the starter motor. The sensor detects the crankshaft position without contact (Hall effect) by means of missing segments on the tone wheel behind flex plate. The electronic control module (ECM) detects TDC position of cylinder 1 by means of the signal supplied by the sensor. Injection timing is synchronized by means of the camshaft signal and the crankshaft signal. This sensor is used to detect engine speed.

When the crankshaft rotates, an alternating voltage is generated in the crankshaft position sensor by the gaps of the tone wheel located behind the flex plate. In this case, the metal portion of the tone wheel generates a positive voltage pulse and the gap in the tone wheel a negative voltage pulse. The distance from the positive to the negative voltage peak equals the length of the gap.

The gap created by 3 missing teeth has the effect that no voltage is generated in the crankshaft position sensor. The ECM analyzes this gap, or time, without a signal from the crankshaft sensor, in order to detect the TDC position of cylinder 1.

Removal & Installation



3.7L
  1. Clean out machined hole in engine block.
  2.  
  3. Apply a small amount of engine oil to sensor O-ring.
  4.  
  5. Install sensor into engine block with a slight rocking and twisting action.
    WARNING
    Before tightening sensor mounting bolt, be sure sensor is completely flush to cylinder block. If sensor is not flush, damage to sensor mounting tang may result.

  6.  
  7. Install mounting bolt and tighten to 28 Nm (21 ft. lbs.) torque.
  8.  
  9. Connect electrical connector to sensor.
  10.  

4.0L Engine

New replacement sensors will be equipped with a paper spacer glued to bottom of sensor. If installing (returning) a used sensor to vehicle, a new paper spacer must be installed to bottom of sensor. This spacer will be ground off the first time engine is started. If spacer is not used, sensor will be broken the first time engine is started.

New Sensors: Be sure paper spacer is installed to bottom of sensor. If not, obtain spacer PN05252229.

Used Sensors: Clean bottom of sensor and install spacer PN05252229.

  1. Install sensor into transmission bellhousing hole.
  2.  
  3. Position sensor wire shield to sensor.
  4.  
  5. Push sensor against flywheel/drive plate. With sensor pushed against flywheel/drive plate, tighten mounting bolt to 7 Nm (60 inch lbs.) torque.
  6.  
  7. Route sensor wiring harness into wire shield.
  8.  
  9. Connect sensor pigtail harness electrical connector to main wiring harness.
  10.  

4.7L

The Crankshaft Position (CKP) sensor is bolted to the side of the engine cylinder block above the starter motor. It is positioned into a machined hole at the side of the engine block.

  1. Remove starter motor.
  2.  
  3. Disconnect CKP electrical connector at sensor.
  4.  
  5. Remove CKP mounting bolt.
  6.  
  7. Carefully twist sensor from cylinder block.
  8.  
  9. Remove sensor from vehicle.
  10.  
  11. Check condition of sensor O-ring.

    Click image to see an enlarged view

    Fig.

  12.  

5.7L Engine

WARNING
Before tightening sensor mounting bolt, be sure sensor is completely flush to cylinder block. If sensor is not flush, damage to sensor mounting tang may result.

  1. Clean out machined hole in engine block.
  2.  
  3. Apply a small amount of engine oil to sensor O-ring.
  4.  
  5. Install sensor (4) into engine block with a slight rocking and twisting action.
  6.  
  7. Install mounting bolt and tighten to 28 Nm (21 ft. lbs.) torque.
  8.  
  9. Connect electrical connector (2) to sensor.
  10.  
  11. Lower vehicle.
  12.  

 
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