GM Bonneville/Eighty Eight/LeSabre 1986-1999

Camshaft Position Sensor

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OPERATION



See Figures 1 and 2

The PCM uses the Camshaft Position (CMP) sensor to determine the position of the No. 1 piston during its power stroke. This signal is used by the PCM to calculate the fuel injection mode of operation.

If the camshaft signal is lost while the engine is running, the fuel injection system will shift to a calculated fuel injected mode based on the last fuel injection pulse, and the engine will continue to run.



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Fig. Fig. 1: Typical Camshaft Position (CMP) sensor



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Fig. Fig. 2: Camshaft Position (CMP) and Crankshaft Position (CKP) sensor locations - 1995 vehicle shown, others similar

TESTING



See Figure 3

The best method to test this sensor is with the use of an oscilloscope.

  1. Visually check the connector, making sure it is connected properly and all of the terminals are straight, tight and free of corrosion.
  2.  
  3. With the ignition in the ON position, check the sensor voltage using an oscilloscope. When the starter is briefly operated, a square wave pattern, alternating from 0-12 volts should be seen at terminal A. If the voltage is within specification, the sensor is functional.
  4.  



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Fig. Fig. 3: Camshaft Position (CMP) sensor circuit

  1. If the sensor voltage is not within specifications, use a DVOM to check terminal C for battery positive (B+). If battery positive (B+) voltage is not present, check the circuit continuity and repair as necessary.
  2.  
  3. If battery positive (B+) voltage is present at terminal C, check terminal B for proper ground. If ground is not present, check the circuit for continuity and repair as necessary.
  4.  
  5. If the sensor and circuits are functional, the PCM may be faulty.
  6.  

REMOVAL & INSTALLATION



See Figure 4

  1. Disconnect the negative battery cable.
  2.  
  3. Raise and safely support the vehicle. Remove the right front wheel and tire assembly.
  4.  
  5. Remove the right inner fender access cover/splash shield.
  6.  
  7. Detach the electrical connector from the CMP sensor.
  8.  
  9. Unfasten the retaining screw, then remove the CMP sensor.
  10.  



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Fig. Fig. 4: Exploded view of the Camshaft Position (CMP) sensor mounting

To install:
  1. Install the CMP sensor, and install the retaining screw. Tighten the screw 35-53 inch lbs. (4-6 Nm).
  2.  
  3. Attach the electrical connector to the CMP sensor.
  4.  
  5. Install the right inner splash shield/fender access cover.
  6.  
  7. Install the right front wheel and tire assembly, then carefully lower the vehicle.
  8.  
  9. Connect the negative battery cable.
  10.  

 
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