How to Check a Crank Shaft Sensor

by Jeremy Holt
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circuit board image by Michele Maakestad from

Crankshaft position sensors, or crank sensors, most often use a magnetic or Hall Effect switching device to signal the vehicle's onboard computer with the crankshaft's rotational speed and position. This information is used to regulate ignition and fuel injection timing. They are typically mounted directly on the crankshaft, but other locations include: on the main crank pulley, near the flywheel, or mounted to the engine block near the water pump. A malfunctioning crank sensor will cause the engine to idle and accelerate inconsistently, misfire and even shut off intermittently. It is possible to check the operation of the crank sensor using a voltmeter. This process requires solid automotive experience and knowledge.

Voltage Check

Step 1

Turn the ignition on but do not start the engine.

Step 2

Raise the vehicle's hood and prop it open. Locate the crank sensor and disconnect its electrical connector.

Place the prongs of a voltmeter onto the terminals in the wiring harness to test for battery voltage to the crank sensor. If zero voltage is recorded there is a fault in the wiring from the battery to the sensor.

Sensor Check

Step 1

Attach a socket and breaker bar to the nut that holds the crankshaft pulley to the engine block.

Step 2

Connect a voltmeter set to the AC scale to the crank sensor. Have an assistant slowly rotate the pulley gear clockwise with the breaker bar.

Take a reading from the voltmeter. A pulsing voltage of between zero and 0.05 volts indicates the sensor is operating normally. If no voltage is recorded the sensor is malfunctioning.

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