Ram B1500, B2500, B3500, 1999-2003

Camshaft Position Sensor

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Description & Operation



The Camshaft Position (CMP) sensor provides camshaft position information that is used by the ECM for fuel and ignition system synchronization. The sensor is a Hall effect digital sensor. It has a metal pulse ring and a pickup assembly located inside the distributor. The CMP signal is a digital on/off type signal. When the pulse ring travels through the pickup, a permanent magnet inside the pickup creates magnetism, which induces voltage. The pulse ring has slots, or one large slot; as the slot(s) pass, the pickup loses its magnetism and voltage is lost, thereby generating the on/off signal. The CMP and Crankshaft Position (CKP) sensor let the ECM know the position of the camshaft and crankshaft, so the engine can be properly timed.

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Fig.

The Camshaft Position (CMP) sensor provides camshaft position information that is used by the ECM for fuel and ignition system synchronization. The sensor is a Hall effect digital sensor. It has a metal pulse ring and a pickup assembly located inside the distributor. The CMP signal is a digital on/off type signal. When the pulse ring travels through the pickup, a permanent magnet inside the pickup creates magnetism, which induces voltage. The pulse ring has slots, or one large slot; as the slot(s) pass, the pickup loses its magnetism and voltage is lost, thereby generating the on/off signal. The CMP and Crankshaft Position (CKP) sensor let the ECM know the position of the camshaft and crankshaft, so the engine can be properly timed.

Click image to see an enlarged view

Fig.

The camshaft position sensor is required for all vehicles that utilize a sequential multi-port fuel injection system. It serves this system by providing a fuel sync signal to the engine controller. The sync signal is used in conjunction with the signal sent by the crankshaft signal to maintain the correct injector firing order.



On 2.5L, 3.9L, 5.2L and 5.9L gasoline engines, the camshaft position sensor is located in the distributor
 
On the 4.7L engine, the camshaft sensor is bolted to the front top of the right-hand cylinder head
 
On V-10 engines, the camshaft position sensor is found in the timing chain case/cover on the left-front side of the engine
 
On diesel engines, the sensor is located below the fuel injection pump and is attached to the back of the timing gear cover housing
 



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Fig. Exploded view of the camshaft position sensor mounting-2.5L, 3.9L, 5.2L, 5.9L engines



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Fig. Camshaft position sensor mounting-V-10 engine



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Fig. Camshaft sensor components-V-10 engine

Removal & Installation



  1. Disconnect the negative battery cable.
  2.  
  3. Locate the sensor. Disconnect the wiring.
  4.  
  5. Remove the mounting screws and pull off the sensor.
  6.  
  7. Check condition of any seals or O-rings.
  8.  
  9. Installation is the reverse of removal.
  10.  



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Fig. Detach the CMP's sensor connector-5.2L engine shown



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Fig. The CMP sensor pickup removed from the distributor. Note the pulse ring on the distributor shaft

2.5L, 3.9L, 5.2L, 5.9L Gasoline Engines
  1. Remove the air cleaner assembly.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Remove the distributor cap and unplug the camshaft position sensor wire.
  6.  
  7. Remove the rotor from the shaft, and then lift the camshaft position sensor assembly from the distributor.
  8.  

To install:

  1. Install the camshaft position sensor, aligning the sensor notch to the housing.
  2.  
  3. Connect the wire, install the rotor and cap.
  4.  
  5. Install the air cleaner assembly, if removed.
  6.  

Sensor Replacement (8.0L)-New Sensor

Use this procedure if a NEW camshaft position sensor is to be installed.

  1. Unplug the wire connectors and unbolt the sensor.
  2.  
  3. Carefully pry the sensor from the timing chain case/cover in a rocking action with two small prytools.
  4.  
  5. Remove the sensor. Check the condition of the sensor O-ring.
  6.  

To install:

  1. Lightly lubricate the O-ring with fresh engine oil.
  2.  
  3. Using a slight rocking action, install the sensor into the timing case/cover until the paper spacer just contacts the gear. Do NOT twist the sensor or you may tear the O-ring. Push the sensor all the way into the cover until the rib material on the sensor contacts the camshaft gear.
  4.  
  5. Install the mounting bolt, tightening it to 50 inch lbs. (6 Nm).
  6.  
  7. Connect the sensor wiring.
  8.  



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Fig. Sensor depth positioning rib-8.0L engine: sensor (1), paper spacer (2), rib for sensor depth positioning (3)

Sensor Replacement (8.0L)-Old Sensor

A thin plastic rib is molded into the face of the camshaft position sensor to position the depth of the sensor to the upper cam gear (sprocket). This rib is found on original and replacement sensors. The first time the engine is operated with the new sensor, part of the rib may be sheared (ground) off. Depending on parts tolerances, some of the plastic rib may still be observed after removal.


NOTE
This procedure will require a special peel-and-stick paper spacer of a calibrated thickness for setting the tolerance of the sensor upon installation. This special paper should be available from the dealer parts department.

If the original camshaft position sensor is to be removed and installed, such as when servicing the timing chain, timing gears or timing chain cover, use this procedure.

  1. Unplug the sensor harness connector from the engine harness.
  2.  
  3. Remove the sensor mounting bolt.
  4.  
  5. Carefully pry the sensor from the timing chain case/cover in a rocking action with two small prytools.
  6.  
  7. Remove the sensor. Check the condition of the sensor O-ring.
  8.  

To install:


NOTE
When installing a used camshaft position sensor, the depth must be adjusted.

  1. Inspect the face of the sensor. If any of the original rib material remains, cut it flush to the face of the sensor with a razor knife. Remove only enough of the rib material until the face is flat.
  2.  


WARNING
Do NOT remove more rib material than necessary or damage to the sensor may result. NEVER use an electric grinder to remove rib material, as the magnetic field from the electric motor may cause electrical damage to the sensor.

  1. Apply the special peel-and-stick paper spacer to the (clean and flat) face of the sensor.
  2.  
  3. Apply a small amount of clean engine oil to the O-ring.
  4.  
  5. Using a slight rocking action, install the sensor into the timing case/cover until the paper spacer just contacts the gear. Do NOT twist the sensor or you may tear the paper or O-ring. Do NOT install the mounting bolt.
  6.  
  7. Use a scribe to scratch a line into the timing case/cover to indicate the depth of the sensor, then remove the sensor.
  8.  
  9. Remove the paper spacer so it will not remain in the engine and get lost in the engine oil passages.
  10.  
  11. Again, apply a small amount of oil to the sensor O-ring and install the sensor until it aligns with the scribe mark.
  12.  
  13. Install the mounting bolt, tightening it to 50 inch lbs. (6 Nm).
  14.  
  15. Plug-in the engine wire harness connector to the sensor connector.
  16.  

Testing




WARNING
Testing the wiring harness with the ECM still connected can cause serious damage to the processor. ALWAYS disconnect the ECM before Testing the wiring harness., unless instructed otherwise.

  1. Remove the engine cover.
  2.  
  3. With the DRB-II scan tool or equivalent, plug in to diagnostic connector.
  4.  
  5. Using the DRB-II, erase all DTCs and turn the ignition off and on again.
  6.  
  7. Crank the engine and observe CAM SYNC; if NO CAM SYNC is shown, proceed to the next step. If CAM SYNC was present, the CMP sensor is operational.
  8.  
  9. Inspect the wiring and connectors, repair as necessary and retest or if OK, proceed to next step.
  10.  
  11. Unplug the CMP sensor connector.
  12.  
  13. Turn the ignition ON and, using a voltmeter, probe the CMP connector to verify the supply voltage using supplied wiring schematic.
  14.  
  15. On 1995 and earlier vehicles, if voltage is 7.0v or above, proceed to the next step; if no voltage or insufficient voltage is detected, repair the circuit and retest.
  16.  
  17. On 1996-98 vehicles, the voltage should be 4.5v or above. If voltage does not met specifications, repair circuit and retest, if OK, proceed to next step.
  18.  
  19. Connect a jumper between the CMP signal circuit and CMP ground circuit (use supplied schematic). Without turning key off, attempt to start vehicle while making and breaking connection. If vehicle starts, replace CMP sensor. If vehicle does not start proceed to next step.
  20.  
  21. Remove the distributor cap and ensure that distributor turns while cranking engine. If distributor turns, proceed to next step, if it does not turn, repair as necessary and retest.
  22.  
  23. Disconnect the negative battery cable.
  24.  
  25. Using an ohmmeter, probe the ground circuit between the CMP sensor connector and a engine ground. If resistance is less than 5.0 ohms, proceed to next step, if not, repair circuit and retest.
  26.  
  27. Disconnect the ECM wiring harness.
  28.  
  29. Using an ohmmeter, test the CMP signal circuit for resistance between the CMP sensor connector and the ECM harness connector. If resistance is less than 5.0 ohms, proceed to next step, if not, repair circuit and retest.
  30.  
  31. Using an ohmmeter measure the CMP signal circuit resistance between CMP connector and ground, if resistance is less than 5.0 ohms, repair the CMP signal circuit for a short ground. If the resistance is more than 5.0 ohms, replace the ECM.
  32.  
  33. Install the engine cover. Connect the negative battery cable.

    Click image to see an enlarged view

    Fig.

  34.  


WARNING
Testing the wiring harness with the ECM still connected can cause serious damage to the processor. ALWAYS disconnect the ECM before Testing the wiring harness., unless instructed otherwise.

  1. Remove the engine cover.
  2.  
  3. With the DRB-II scan tool or equivalent, plug in to diagnostic connector.
  4.  
  5. Using the DRB-II, erase all DTCs and turn the ignition off and on again.
  6.  
  7. Crank the engine and observe CAM SYNC; if NO CAM SYNC is shown, proceed to the next step. If CAM SYNC was present, the CMP sensor is operational.
  8.  
  9. Inspect the wiring and connectors, repair as necessary and retest or if OK, proceed to next step.
  10.  
  11. Unplug the CMP sensor connector.
  12.  
  13. Turn the ignition ON and, using a voltmeter, probe the CMP connector to verify the supply voltage using supplied wiring schematic.
  14.  
  15. On 1995 and earlier vehicles, if voltage is 7.0v or above, proceed to the next step; if no voltage or insufficient voltage is detected, repair the circuit and retest.
  16.  
  17. On 1996-98 vehicles, the voltage should be 4.5v or above. If voltage does not met specifications, repair circuit and retest, if OK, proceed to next step.
  18.  
  19. Connect a jumper between the CMP signal circuit and CMP ground circuit (use supplied schematic). Without turning key off, attempt to start vehicle while making and breaking connection. If vehicle starts, replace CMP sensor. If vehicle does not start proceed to next step.
  20.  
  21. Remove the distributor cap and ensure that distributor turns while cranking engine. If distributor turns, proceed to next step, if it does not turn, repair as necessary and retest.
  22.  
  23. Disconnect the negative battery cable.
  24.  
  25. Using an ohmmeter, probe the ground circuit between the CMP sensor connector and a engine ground. If resistance is less than 5.0 ohms, proceed to next step, if not, repair circuit and retest.
  26.  
  27. Disconnect the ECM wiring harness.
  28.  
  29. Using an ohmmeter, test the CMP signal circuit for resistance between the CMP sensor connector and the ECM harness connector. If resistance is less than 5.0 ohms, proceed to next step, if not, repair circuit and retest.
  30.  
  31. Using an ohmmeter measure the CMP signal circuit resistance between CMP connector and ground, if resistance is less than 5.0 ohms, repair the CMP signal circuit for a short ground. If the resistance is more than 5.0 ohms, replace the ECM.
  32.  
  33. Install the engine cover. Connect the negative battery cable.

    Click image to see an enlarged view

    Fig.

  34.  

To completely test this sensor and circuitry, you need the DRBII scan tool, or equivalent. This is a test of the camshaft position sensor only.

For this test you will need an analog (non-digital) voltmeter. Do NOT remove the distributor connector. Using small paper clips, insert them into the backside of the distributor wire harness connector to make contact with the terminals. Do NOT damage the connector when inserting the paper clips. Attach the voltmeter leads to these clips.

  1. Connect the positive voltmeter lead to the sensor output wire.
  2.  
  3. Connect the negative voltmeter lead to the ground wire.
  4.  



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Fig. Camshaft Position Sensor circuit schematic



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Fig. Camshaft Position Sensor wires: (1) ORN (5v supply), (2) BK/LB (sensor ground), (3) TN/YL (camshaft position sensor signal)

  1. Turn the ignition ON . Rotate the engine. The meter should show a reading of less than 1 volt and a high voltage reading of 5.0 volts as the high and low points on the wheel pass the sensor.
  2.  
  3. If there is no voltage reading at all, check the meter connections.
  4.  
  5. If voltage is still not present, check for voltage at the supply wire.
  6.  
  7. If 5.0 volts is not found at the supply wire, check for voltage at cavity A-17 of the 32-way connector. Leave the engine controller harness connected for this test.
  8.  


NOTE
If voltage is not found at the PCM connector, you will need to diagnose the system using a DRBII scan tool, or equivalent, or take the vehicle to a qualified shop.

  1. If voltage is present at the engine controller connector, but not the supply wire:
    1. Check continuity between the sensor and supply wire. This is checked between the distributor connector and cavity A-17 . If continuity is not present, repair the wire harness.
    2.  
    3. Check for continuity between the camshaft position sensor output wire and cavity A-18 at the engine controller. If continuity is not present, repair the wire harness.
    4.  
    5. Check for continuity between the ground circuit wire at the distributor connector and ground. If continuity is not present, repair the wire harness.
    6.  

  2.  
  3. Crank the engine while observing the voltmeter. The voltmeter needle should fluctuate 0-5 volts, approximately. This will verify the camshaft position sensor is operating properly and a sync pulse signal is being generated.
  4.  
  5. If a sync pulse signal is not detected, and all other variables have been eliminated, replace the camshaft position sensor.
  6.  

 
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