Five Hundred, Mercury Montego 2005

Crankshaft Position Sensor



The Crankshaft Position (CKP) sensor is a variable reluctance sensor that uses a trigger wheel to induce voltage. The CKP sensor is a fixed magnetic sensor mounted to the engine block and monitors the trigger or "pulse" wheel which is attached to the crank pulley/damper. As the pulse wheel rotates by the CKP sensor, teeth on the pulse wheel induce voltage inside the sensor through magnetism. The pulse wheel has a missing tooth that changes the reading of the sensor. This is used for the Cylinder Identification (CID) function to properly monitor and adjust engine timing by locating the number 1 cylinder. The voltage created by the CKP sensor is alternating current (A/C). This voltage reading is sent to the PCM and is used to determine engine RPM, engine timing, and is used to fire the ignition coils.

Removal & Installation

  1. With vehicle in NEUTRAL, position it on a hoist.
  3. Disconnect the negative battery cable.
  5. Remove the 7 pin-type retainers and the right side splash shield.
  7. Disconnect the crankshaft position (CKP) sensor electrical connector.
  9. Remove the bolt and the CKP sensor.

To install:

  1. Installation is the reverse of removal.


Click image to see an enlarged view

Fig. Test the CKP sensor for output voltage while the engine is cranked or running. Voltage should be more

  1. Measure the voltage between the sensor CKP sensor terminals by backprobing the sensor connector.
  3. If the connector cannot be backprobed, fabricate or purchase a test harness.
  5. Sensor voltage should be more than 0.1 volt AC with the engine running and should vary with engine RPM.
  7. If voltage is not within specification, the sensor may be faulty.