How to Replace a GMC Sierra Crank Sensor

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The crank sensor (properly known as the crankshaft position sensor or CKP) on a GMC Sierra is a small magnetic sensor that measures the rotation of the crankshaft. The crank sensor measures engine RPMs and then relays that information to the engine control computer. This helps the engine control computer to set ignition timing, as well as reduce emissions and increase fuel economy. Replacing the crank sensor is a simple task that can be completed within an hour or two.

Things You'll Need

  • Wrench set
  • Socket set
  • GM scan tool
  • Clean engine oil

Removing the Crank Sensor

  • Lift the vehicle according to instructions listed in the owner's manual and support with jack stands underneath the frame.

  • Locate the crankshaft position sensor. On 8.1L engines, it will be on the rear of the engine above the transmission mounting flange. On 4.8L, 5.3L, 6.0L and 6.2L engines, it will be on the side of the engine block above the starter. On all other engines, it will be next to the crankshaft pulley on the left (when standing in front of the vehicle and looking toward the engine) side of the engine block.

  • On 4.8L, 5.3L, 6.0L and 6.2L engines, remove the starter. Remove the two bolts that connect the starter to the engine block. Lower the starter and separate the electrical connector.

  • Remove the bolt that secures the crankshaft sensor to the engine block.

  • Remove the sensor from the engine block. Discard the rubber O-ring.

Installing a Crank Sensor

  • Lubricate the new O-ring with clean engine oil and install it onto the new sensor.

  • Slide the new sensor into the engine block.

  • Reinstall the bolt that retains the sensor in the engine block.

  • Reconnect the wiring connector to the sensor.

  • On 4.8L, 5.3L, 6.0L and 6.2L engines, reinstall the starter. Connect the wiring connector to the starter, then lift it into position. Reinstall the bolts that connect the bolts to the engine block.

  • Connect a GM scan tool to the vehicle's diagnostic port and run the crankshaft position sensor variation learn procedure.

Tips & Warnings

  • Clean the area around the sensor before removing it to prevent dirt, oil or grease from entering the engine block.
  • Always follow instructions listed in the owner's manual when lifting and lowering a vehicle. Failing to do so can cause injury or death.

References

  • "Chilton General Motors Service Manual 2008 Edition Vol. II"; Chilton; 2008
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