GM Full-Size Trucks 1988-1998 Repair Information

Crankshaft Position (CKP) Sensor

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OPERATION



See Figure 1

The Crankshaft Position (CKP) Sensor provides a signal through the ignition module which the ECM uses as a reference to calculate rpm and crankshaft position.



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Fig. Fig. 1: Crankshaft Position (CKP) sensor

TESTING



See Figure 2

  1. Disconnect the CKP sensor harness. Connect an LED test light between battery ground and CKP harness terminal A.
  2.  
  3. With the ignition ON and the engine off, verify that the test light illuminates.
  4.  
  5. If not as specified, repair or replace the fuse and/or wiring.
  6.  
  7. Carefully connect the test light between CKP harness terminal A and B. Verify that the test light illuminates.
  8.  



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Fig. Fig. 2: Crankshaft Position (CKP) sensor wiring diagram

  1. If not as specified, repair the CKP harness ground circuit (terminal B).
  2.  
  3. Turn the ignition OFF and disconnect the test light.
  4.  
  5. Next, connect suitable jumper wires between the CKP sensor and CKP sensor harness. Connect a duty cycle meter to the jumper wire corresponding to CKP terminal C and battery ground.
  6.  
  7. Crank the engine and verify that the duty cycle signal is between 40-60%.
  8.  
  9. If it is not as specified, the CKP sensor may be faulty.
  10.  
  11. Next, connect a AC volt meter to the jumper wire corresponding to CKP terminal C and battery ground.
  12.  
  13. Crank the engine and verify that the AC voltage signal is at least 10.0 volts.
  14.  
  15. If not as specified the CKP sensor may be faulty.
  16.  

REMOVAL & INSTALLATION



  1. Disconnect the negative battery cable.
  2.  
  3. Detach the sensor harness connector at the sensor.
  4.  
  5. Unfasten the retaining bolt, then remove the sensor from the front cover. Inspect the sensor O-ring for wear, cracks or leakage and replace if necessary.
  6.  

To install:
  1. Lubricate the O-ring with clean engine oil, then place on the sensor. Install the sensor into the front cover.
  2.  
  3. Install the sensor and tighten the retaining bolt.
  4.  
  5. Attach the sensor harness connector.
  6.  
  7. Connect the negative battery cable.
  8.  

 
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