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    1969 Lincoln Mark III 7.5L 4BL OHV 8cyl

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    Envoy, Rainer, Trailblazer 2006-2007

    Camshaft Position Sensor

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    Description & Operation



    4.2L Engine

    The Camshaft Position (CMP) sensor is triggered by a notched reluctor wheel built into the exhaust camshaft sprocket. The CMP sensor provides 6 signal pulses every camshaft revolution. Each notch, or feature of the reluctor wheel is of a different size for individual cylinder identification. This means the CMP and Crankshaft Position (CKP) signals are pulse width encoded to enable the powertrain control module (PCM) to constantly monitor their relationship. This relationship is used to determine camshaft actuator position and control its phasing at the correct value. The PCM also uses this signal to identify the compression stroke of each cylinder, and for sequential fuel injection. The CMP sensor is connected to the PCM by a 12-volt, low reference, and signal circuit.

    5.3L Engine

    The Camshaft Position (CMP) sensor is also a magneto resistive sensor, with the same type of circuits as the Crankshaft Position (CKP) sensor. The CMP sensor signal is a digital ON/OFF pulse, output once per revolution of the camshaft. The CMP sensor information is used by the engine control module (ECM) to determine the position of the valve train relative to the CKP.

    6.0L Engine

    The Camshaft Position (CMP) sensor is a 3-wire sensor that provides a digital output signal. The wire circuits consist of an engine control module (ECM) supplied 5-volt reference circuit, a low reference circuit between the CMP sensor and the ECM, and an output signal circuit from the CMP sensor to the ECM. The CMP sensor detects magnetic flux changes between the teeth and slots on the 4-tooth reluctor wheel. The CMP sensor provides a digital ON/OFF DC voltage of varying frequency, with 4 varying width output pulses, per each camshaft revolution. The frequency of the CMP sensor output signal depends on the speed of the camshaft. The ECM will recognize the narrow and wide tooth patterns to identify camshaft position, or which cylinder is in compression and which is in exhaust. The information is then used to determine the correct time and sequence for fuel injection and ignition spark events. The ECM also uses the CMP sensor output signal to determine the camshaft relative position to the crankshaft position.

    Removal & Installation



    4.2L Engine
    1. Disconnect the negative battery cable.
    2.  
    3. Remove the Camshaft Position (CMP) sensor electrical connector (1).
    4.  
    5. Remove the CMP sensor retaining bolt.

      Click image to see an enlarged view

      Fig. Location of the Camshaft Position (CMP) sensor (1)-4.2L engine

    6.  

    To install:

    1. Install the CMP sensor and tighten the CMP sensor bolt to 89 inch lbs. (10 Nm).
    2.  
    3. Install the CMP sensor electrical connector (1).
    4.  
    5. Connect the negative battery cable.
    6.  

    5.3L And 6.0L Engines
    1. Disconnect the negative battery cable.
    2.  
    3. Remove the alternator bracket assembly.
    4.  
    5. Remove the Camshaft Position (CMP) sensor mounting bolts (1).
    6.  
    7. Remove the CMP sensor assembly (4, 5, 6) from the front cover (7).
    8.  
    9. Disconnect the CMP sensor jumper harness (2) and the engine harness (3) electrical connectors.
    10.  
    11. Remove the CMP sensor assembly (4, 5, 6).
    12.  
    13. Disconnect CMP sensor (5) from the jumper harness (4).

      Click image to see an enlarged view

      Fig. Location of the Camshaft Position (CMP) sensor (5) and related components-5.3L and 6.0L engines

    14.  

    To install:

    1. Reconnect the CMP sensor (5) and the jumper harness (4).
    2.  
    3. Install the O-ring (6) on the CMP sensor assembly (4, 5).
    4.  
    5. Reconnect the CMP sensor assembly (4, 5, 6) and the engine harness connector (3).
    6.  
    7. Install the CMP sensor assembly (4, 5, 6) in the front cover (7). Apply a small amount of clean motor oil to the O-ring (6).
    8.  
    9. Install the CMP sensor mounting bolts and tighten them to 18 ft. lbs. (25 Nm).
    10.  
    11. Install the alternator assembly.
    12.  
    13. Connect the negative battery cable.
    14.  

    Testing



    4.2L Engine


    Click image to see an enlarged view

    Fig. Camshaft Position (CMP) sensor electrical connector end view-4.2L engine

    1. Inspect the Camshaft Position (CMP) sensor circuits for the following conditions:

      Routed too close to the ignition coils
       
      Routed too close to after-market electrical equipment
       
      Routed too close to solenoids, relays, and motors
       

    2.  
    3. If such conditions do not exist, proceed to the next step.
    4.  
    5. Test for an intermittent and for a poor connection at the CMP sensor. If such conditions do not exist, proceed to the next step.
    6.  
    7. Test for an intermittent and for a poor connection at the Powertrain Control Module (PCM). If such conditions do not exist, proceed to the next step.
    8.  
    9. Remove the CMP sensor.
    10.  
    11. Inspect the CMP sensor and the camshaft reluctor wheel for the following conditions:

      Incorrect sensor installation
       
      A cracked or broken sensor
       
      The sensor coming in contact with the reluctor wheel
       
      Excessive air gap between the reluctor wheel and the sensor
       
      Foreign material passing between the sensor and the camshaft reluctor wheel
       
      Missing teeth in the camshaft reluctor wheel
       

    12.  
    13. If none of these conditions exists, proceed to the next step.
    14.  
    15. Replace the CMP sensor.
    16.  
    17. Using a scan tool, clear any Diagnostic Trouble Codes (DTC).
    18.  
    19. Turn OFF the ignition for 30 seconds.
    20.  
    21. Start the engine.
    22.  
    23. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
    24.  
    25. Observe the Capture Info with a scan tool.
    26.  
    27. Check for any undiagnosed DTCs.
    28.  

    5.3L & 6.0L Engines


    Click image to see an enlarged view

    Fig. Camshaft Position (CMP) sensor electrical connector end view-5.3L and 6.0L engines

    1. Start and idle the engine.
    2.  
    3. Monitor the Camshaft Position (CMP) sensor active counter parameter with a scan tool.
    4.  
    5. If the CMP sensor active counter number increment, test for intermittent poor connection. If it tests okay, proceed to the next step.
    6.  
    7. Turn OFF the ignition.
    8.  
    9. Disconnect the CMP sensor electrical connector.
    10.  
    11. Test for shorted terminals and poor connections at the CMP sensor wire harness electrical connector and the mating electrical connector on the CMP sensor.
    12.  
    13. If such conditions do not exist, proceed to the next step.
    14.  
    15. Turn ON the ignition, with the engine OFF.
    16.  
    17. Connect a jumper wire to the 12V reference circuit at the CMP sensor wire harness electrical connector.
    18.  
    19. Connect a test lamp between the jumper wire and a good ground.
    20.  
    21. Connect the positive lead of the Digital Multi-Meter (DMM) to the junction of the jumper wire and test lamp.
    22.  
    23. Connect the negative lead of the DMM to a good engine ground.
    24.  
    25. Measure the voltage from the 12V reference circuit to a good ground with a DMM.
    26.  
    27. If the voltage measures out of the specified range (10-13V), test the CMP 12V reference circuit between the CMP sensor and the Engine Control Module (ECM) for an open, high resistance and short-to-ground. If the voltage measures within 10-13V proceed to the next step.
    28.  
    29. Remove the test lamp from the jumper wire.
    30.  
    31. Connect another jumper wire to the signal circuit of the CMP sensor wire harness electrical connector.
    32.  
    33. Turn ON the ignition, with the engine OFF.
    34.  
    35. Monitor the CMP active counter parameter with a scan tool.
    36.  
    37. Momentarily connect the two ends of the jumper wires together several times.
    38.  
    39. If the CMP sensor active counter number increment, replace the CMP sensor.
    40.  
    41. Using a scan tool, clear any Diagnostic Trouble Codes (DTC).
    42.  
    43. Turn OFF the ignition for 30 seconds.
    44.  
    45. Start the engine.
    46.  
    47. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
    48.  
    49. Observe the Capture Info with a scan tool.
    50.  
    51. Check for any undiagnosed DTCs.
    52.  

     
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