Breeze, Cirrus, Sebring Convertible and Sedan, Stratus Sedan, 1999-2005

Camshaft Position Sensor

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Description & Operation



Not for Dodge Stratus Sedan

The CMP sensor contains a Hall-effect device that provides cylinder identification to the Powertrain Control Module (PCM). The sensor generates pulses as groups of notches on the camshaft sprocket pass underneath it. The PCM keeps track of crankshaft rotation and identifies each cylinder by the pulses generated by the notches on the camshaft sprocket. Crankshaft pulses follow each group of camshaft pulses.

The camshaft position sensor (along with the crankshaft position sensor) provides inputs to the PCM to determine fuel injection synchronization and cylinder identification. From these inputs, the PCM determines crankshaft position.

On 4-cylinder engines, the camshaft position sensor mounts to the rear of the cylinder head. The sensor also serves as a thrust plate to control endplay of the camshaft.

The 6-cylinder engines are equipped with a camshaft driven mechanical distributor, which is equipped with an internal camshaft position (fuel sync) sensor.

Click image to see an enlarged view

Fig.



Click image to see an enlarged view

Fig.

The CMP sensor contains a Hall-effect device that provides cylinder identification to the Powertrain Control Module (PCM). The sensor generates pulses as groups of notches on the camshaft sprocket pass underneath it. The PCM keeps track of crankshaft rotation and identifies each cylinder by the pulses generated by the notches on the camshaft sprocket. Crankshaft pulses follow each group of camshaft pulses.

Removal & Installation



  1. The camshaft position sensor is mounted in the front of the head.
  2.  
  3. Disconnect electrical connector from sensor.
  4.  
  5. Remove camshaft position sensor screw.
  6.  
  7. Without pulling on the connector, pull the sensor out of the chain case cover.
  8.  

To Install:

  1. Install sensor in the chain case cover and push sensor in until contact is made with the boss on the head.
  2.  
  3. While holding the sensor in this position, install and tighten the retaining bolt to 12 Nm (105 inch lbs.) torque.
  4.  
  5. Attach electrical connector to sensor.
  6.  
  7. Install the sensor.
  8.  

  1. The camshaft position sensor is mounted in the front of the head.
  2.  
  3. Disconnect electrical connector from sensor.
  4.  
  5. Remove camshaft position sensor screw.
  6.  
  7. Without pulling on the connector, pull the sensor out of the chain case cover.
  8.  

To Install:

  1. Install sensor in the chain case cover and push sensor in until contact is made with the boss on the head.
  2.  
  3. While holding the sensor in this position, install and tighten the retaining bolt to 12 Nm (105 inch lbs.) torque.
  4.  
  5. Attach electrical connector to sensor.
  6.  
  7. Install the sensor.
  8.  

Testing



Not for Dodge Stratus Sedan

  1. Disconnect the camshaft position sensor connector, and connect the test harness special tool (MB991709) in between. (All terminals should be connected.)
  2.  
  3. Connect the oscilloscope probe to camshaft position sensor connector terminal 2.
  4.  
  5. Disconnect the crankshaft position sensor connector, and connect the test harness special tool (MD998478) in between.
  6.  
  7. Connect the oscilloscope probe to crankshaft position sensor connector terminal 2 (black clip of special tool).
  8.  

When metal aligns with the sensor, voltage goes low (less than 0.3 volts). When a notch aligns with the sensor, voltage spikes high (5.0 volts). As a group of notches pass under the sensor, the voltage switches from low (metal) to high (notch) then back to low. The number of notches determines the amount of pulses. If available, an oscilloscope or scan tool with special module can display the square wave patterns of each timing event.

Click image to see an enlarged view

Fig. Camshaft Position Sensor Testing



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Fig. Camshaft Position Sensor Location on 2.7L

Not for Dodge Stratus Sedan

Prior to Testing, ensure the shift selector in Park and block the drive wheels for safety.

Testing the CMP Sensor with a DVOM

This test is used to monitor the DC voltage to look for circuit or sensor faults. If the CMP sensor transistor switches, but cannot pull the signal to ground, the average DC voltage displayed will jump significantly. If the transistor stops switching, the average DC voltage will drop. Because the average voltage is already near 0v, this type of failure is more difficult to find with this test.

Connect the DVOM positive lead to the CMP sensor signal circuit (TN/YL wire) at Pin 1-33 and the negative lead to the battery negative post.

In this example, the display shows the CMP sensor signal at Hot Idle. The DVOM shows a CMP signal of only 0.46v DC because the instrument is averaging the signal voltage. The average value is low because the signal is low much longer than is high (note the 92.1 % duty cycle). Use the DVOM MIN/MAX feature, if available, to verify that the CMP signal is switching from 0-5v.

Note the HZ value in this example is OL. The frequency (Hz) measured by the DVOM could be a useful indicator of an intermittent signal. However, the frequency changes in relation to the camshaft position (number of windows) and can cause the DVOM to be unable to calculate a value. In this case, change the time base from 10 ms/division to 50 or 100 ms/division to have a better chance of seeing a stable and useful value.

Using a Lab Scope to Test the CMP Sensor

The lab scope test is used to monitor this signal over time to verify that the transistor in the sensor continues to toggle the signal from 0-5 volts. Watch for unwanted toggling, failure of the transistor to pull the signal all the way to ground, or intermittently missing one or more pulses. All of these failures can cause drivability problems, trouble codes and no start conditions, depending on the severity of the failure.

The Lab Scope can be used to test the CMP sensor circuit as it provides a very accurate view of circuit activity and any signal glitches. Place the shift selector in Park and block the drive wheels for safety.

Click image to see an enlarged view

Fig.

Connect the Channel A positive probe to the CMP sensor circuit (TN/YL wire) at PCM Pin 1-33, and the negative probe to the battery negative post. Lab Scope Test Example

In the example, the trace shows the CMP sensor signal at Hot Idle. The trace represents 720 of crankshaft rotation, or 360 of camshaft rotation. All six (6) CMP pulses can be seen, in order (1, 2, 3, 1, 3, and 2).

Each group of CMP pulses (1, 2, or 3 pulses) tells the PCM which cylinder is approaching TDC next. The PCM then starts a countdown to TDC using the CKP pulses.

Click image to see an enlarged view

Fig.

To test this sensor, you will need the use of an oscilloscope.

Visually check the connector, making sure it is attached properly and that all of the terminals are straight, tight and free of corrosion. The output voltage of a properly operating camshaft position sensor switches from high (5.0 volts) to low (0.3 volts). By connecting an oscilloscope to the sensor output circuit, you can view the square wave pattern produced by the voltage swing.

  1. Disconnect the camshaft position sensor connector, and connect the test harness special tool (MB991709) in between. (All terminals should be connected.)
  2.  
  3. Connect the oscilloscope probe to camshaft position sensor connector terminal 2.
  4.  
  5. Disconnect the crankshaft position sensor connector, and connect the test harness special tool (MD998478) in between.
  6.  
  7. Connect the oscilloscope probe to crankshaft position sensor connector terminal 2 (black clip of special tool).
  8.  

When metal aligns with the sensor, voltage goes low (less than 0.3 volts). When a notch aligns with the sensor, voltage spikes high (5.0 volts). As a group of notches pass under the sensor, the voltage switches from low (metal) to high (notch) then back to low. The number of notches determines the amount of pulses. If available, an oscilloscope or scan tool with special module can display the square wave patterns of each timing event.

Click image to see an enlarged view

Fig.



Click image to see an enlarged view

Fig.

Prior to Testing, ensure the shift selector in Park and block the drive wheels for safety.

Testing the CMP Sensor with a DVOM

This test is used to monitor the DC voltage to look for circuit or sensor faults. If the CMP sensor transistor switches, but cannot pull the signal to ground, the average DC voltage displayed will jump significantly. If the transistor stops switching, the average DC voltage will drop. Because the average voltage is already near 0v, this type of failure is more difficult to find with this test.

Connect the DVOM positive lead to the CMP sensor signal circuit (TN/YL wire) at Pin 1-33 and the negative lead to the battery negative post.

In this example, the display shows the CMP sensor signal at Hot Idle. The DVOM shows a CMP signal of only 0.46v DC because the instrument is averaging the signal voltage. The average value is low because the signal is low much longer than is high (note the 92.1 % duty cycle). Use the DVOM MIN/MAX feature, if available, to verify that the CMP signal is switching from 0-5v.

Note the HZ value in this example is OL. The frequency (Hz) measured by the DVOM could be a useful indicator of an intermittent signal. However, the frequency changes in relation to the camshaft position (number of windows) and can cause the DVOM to be unable to calculate a value. In this case, change the time base from 10 ms/division to 50 or 100 ms/division to have a better chance of seeing a stable and useful value.

Using a Lab Scope to Test the CMP Sensor

The lab scope test is used to monitor this signal over time to verify that the transistor in the sensor continues to toggle the signal from 0-5 volts. Watch for unwanted toggling, failure of the transistor to pull the signal all the way to ground, or intermittently missing one or more pulses. All of these failures can cause drivability problems, trouble codes and no start conditions, depending on the severity of the failure.

The Lab Scope can be used to test the CMP sensor circuit as it provides a very accurate view of circuit activity and any signal glitches. Place the shift selector in Park and block the drive wheels for safety.

Click image to see an enlarged view

Fig.

Connect the Channel A positive probe to the CMP sensor circuit (TN/YL wire) at PCM Pin 1-33, and the negative probe to the battery negative post. Lab Scope Test Example

In the example, the trace shows the CMP sensor signal at Hot Idle. The trace represents 720 of crankshaft rotation, or 360 of camshaft rotation. All six (6) CMP pulses can be seen, in order (1, 2, 3, 1, 3, and 2).

Each group of CMP pulses (1, 2, or 3 pulses) tells the PCM which cylinder is approaching TDC next. The PCM then starts a countdown to TDC using the CKP pulses.

Click image to see an enlarged view

Fig.

 
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