How to Access a Crankshaft Sensor in a GM 3.8L

Written by cayden conor
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How to Access a Crankshaft Sensor in a GM 3.8L
(IT Stock Free/Polka Dot/Getty Images)

The crankshaft sensor on GM's 3.8-litre engine provides a signal that the ignition-control module uses to calculate the ignition sequence. The ignition control module also uses the signal to send 18X and 3X reference pulses -- a special signal for the programmable control module, or computer -- to calculate engine rpm and the position of the crankshaft. An aluminium mounting bracket holds the crankshaft sensor firmly on the engine, and it is partially hidden by the crankshaft pulley. It has a four-wire harness connector, which provide the signal to the ignition control module.

Skill level:
Moderately Challenging

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Things you need

  • Set of wrenches
  • Set of sockets
  • Ratchet
  • Floor jack
  • Jack stands
  • Lug wrench
  • Flywheel holding device
  • Harmonic balancer removal tool

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  1. 1

    Disconnect the negative battery cable, using a wrench. Set it aside, ensuring that it doesn't touch metal. Check the radiator support, fan shroud or the underside of the hood for a belt routing diagram. If there isn't one, sketch the belt routing on a scrap piece of paper.

  2. 2

    Look at the tensioner pulley -- if it has a bolt in the centre, fit the appropriate socket on it and rotate it toward the centre of the engine to loosen the tension on the belt. If it has a square hole, fit the end of the ratchet into the hole and rotate toward the centre of the engine to loosen tension on the belt. Lift the belt off the crankshaft pulley.

  3. 3

    Raise the front of the vehicle with the floor jack, and support it with jack stands. Remove the right wheel, using the lug wrench. Remove the right inner fender access cover with the appropriate socket.

  4. 4

    Install the flywheel holding device on the flywheel to keep the crankshaft from turning. Remove the crankshaft balancer bolt with a 28-mm socket. Install the harmonic balancer removal tool and turn it clockwise to remove the balancer.

  5. 5

    Remove the circular aluminium shield, or bracket, using the appropriate socket. Take care not to damage the shield. Do not pry on it to remove it. Unplug the wiring harness connector on the crankshaft sensor. Remove the crankshaft sensor retaining bolts.

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