Ram Truck 1500, 2500 & 3500 (2006-2008)

Camshaft Position Sensor

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Description & Operation



3.7L & 4.7L Engines

The Camshaft Position (CMP) sensor on the 3.7L and 4.7L engines contain a hall effect device referred to as a sync signal generator. A rotating target wheel (tonewheel) for the CMP is located at the front of the camshaft for the right cylinder head. This sync signal generator detects notches located on a tonewheel. As the tonewheel rotates, the notches pass through the sync signal generator. The signal from the CMP sensor is used in conjunction with the Crankshaft Position Sensor (CKP) to differentiate between fuel injection and spark events. It is also used to synchronize the fuel injectors with their respective cylinders.

When the leading edge of the tonewheel notch enters the tip of the CMP, the interruption of magnetic field causes the voltage to switch high, resulting in a sync signal of approximately 5 volts

When the trailing edge of the tonewheel notch leaves the tip of the CMP, the change of the magnetic field causes the sync signal voltage to switch low to 0 volts.

5.7L Engine

The CMP sensor is used in conjunction with the crankshaft position sensor to differentiate between fuel injection and spark events. It is also used to synchronize the fuel injectors with their respective cylinders. The sensor generates electrical pulses. These pulses (signals) are sent to the Powertrain Control Module (PCM). The PCM will then determine crankshaft position from both the camshaft position sensor and crankshaft position sensor.

The tonewheel is located at the front of the camshaft. As the tonewheel rotates, notches pass through the sync signal generator.

When the cam gear is rotating, the sensor will detect the notches. Input voltage from the sensor to the PCM will then switch from a low (approximately 0.3 volts) to a high (approximately 5 volts). When the sensor detects a notch has passed, the input voltage switches back low to approximately 0.3 volts.

5.9L & 6.7L Diesel Engines

The Camshaft Position Sensor (CMP) contains a hall effect device. A rotating target wheel (tonewheel) for the CMP is located on the front timing gear. This hall effect device detects notches located on the tonewheel. As the tonewheel rotates, the notches pass the tip of the CMP.

When the leading edge of the tonewheel notch passes the tip of the CMP, the following occurs: The interruption of magnetic field causes the voltage to switch high resulting in a signal of approximately 5 volts.

When the trailing edge of the tonewheel notch passes the tip of the CMP, the following occurs: The change of the magnetic field causes the signal voltage to switch low to 0 volts.

The CMP provides a signal to the Engine Control Module (ECM) at all times when the engine is running. The ECM uses the CMP information primarily on engine start-up. Once the engine is running, the ECM uses the CMP as a backup sensor for engine speed. The Crankshaft Position Sensor (CKP) is the primary engine speed indicator for the engine after the engine is running.

Removal & Installation



3.7L & 4.7L Engines
  1. Before servicing the vehicle, refer to the Precautions section.
  2.  
  3. Disconnect the electrical connector at Camshaft Position (CMP) sensor.
  4.  
  5. Remove the CMP sensor mounting bolt.
  6.  
  7. Carefully twist sensor from cylinder head.
  8.  
  9. Check condition of sensor O-ring.
  10.  

To install:

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

  6.  
  7. Install mounting bolt and tighten to 106 in. lbs. (12 Nm).
  8.  
  9. Connect the electrical connector to sensor.
  10.  

5.7L Engine
  1. Before servicing the vehicle, refer to the Precautions section.
  2.  
  3. Disconnect the electrical connector at Camshaft Position (CMP) sensor.
  4.  
  5. Remove the CMP sensor mounting bolt.
  6.  
  7. Carefully twist CMP sensor from timing gear/chain cover.
  8.  
  9. Check condition of sensor O-ring.
  10.  

To install:

  1. Clean out machined hole in timing gear/chain cover.
  2.  
  3. Install the CMP sensor into timing gear/chain cover with a slight rocking action. Do not twist sensor into position as damage to O-ring may result.
    WARNING
    Before tightening sensor mounting bolt, be sure sensor is completely flush to timing gear/chain cover. If sensor is not flush, damage to sensor mounting tang may result.

  4.  
  5. Install the CMP mounting bolt and tighten to 106 in. lbs. (12 Nm).
  6.  
  7. Connect the electrical connector to the CMP sensor.
  8.  

5.9L & 6.7L Diesel Engines
  1. Before servicing the vehicle, refer to the Precautions section.
  2.  
  3. Disconnect the electrical connector at the Camshaft Position (CMP) sensor.
  4.  
  5. Remove the CMP sensor mounting bolt.
  6.  
  7. Carefully twist sensor from timing gear cover.
  8.  
  9. Check condition of the CMP sensor o-ring.
  10.  

To install:

  1. Clean out machined hole in back of timing gear cover.
  2.  
  3. Apply a small amount of engine oil to sensor o-ring.
  4.  
  5. Install the CMP sensor into timing gear cover with a slight rocking action. Do not twist sensor into position as damage to o-ring may result.
    WARNING
    Before tightening sensor mounting bolt, be sure sensor is completely flush to back of timing chain cover. If sensor is not flush, damage to sensor mounting tang may result.

  6.  
  7. Install mounting bolt and tighten to 106 inch. lbs. (12 Nm).
  8.  
  9. Connect the electrical connector to the CMP sensor.
  10.  

Testing



3.7L, 4.7L & 5.7L Engines
  1. Disconnect the CMP Sensor connector.
  2.  
  3. Ignition on, engine not running.
  4.  
  5. Measure the voltage on the (F856) 5-volt Supply circuit in the CMP harness connector.
  6.  
  7. If the voltage is not between 4.5-5.2 volts. Repair the open or short to ground in the (F856) 5-volt Supply circuit.

    Click image to see an enlarged view

    Fig. Camshaft Position (CMP) sensor electrical connector 3.7L-4.7L-5.7L engines

  8.  

5.9L & 6.7L Diesel Engines
  1. Turn the ignition off.
  2.  
  3. Disconnect the cam sensor harness connector.
    NOTE
    Check connectors and clean or repair as necessary.

  4.  
  5. Measure the resistance between the (F855) 5-volt supply circuit and the (K44) signal circuit of the sensor.
  6.  
  7. If the resistance is not between 900-1100 ohms, replace the camshaft sensor.
  8.  

 
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