How to Check a Camshaft Position Sensor

Written by jeremy holt
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How to Check a Camshaft Position Sensor
The camshaft sensor relays information to the vehicle's on-board computer. (computer circuit board image by glamoroso from Fotolia.com)

There are three main types of camshaft position sensor: the magnetoresistive sensor, the Hall Effect switching device and the magnetic sensor. The camshaft position sensor's main function is to signal the vehicle's on-board computer with the camshaft's rotational speed and position. The computer can then determine various engine functions related to the fuel injection system. A malfunctioning camshaft position sensor may cause the engine to shut off intermittently, or misfire and/or hesitate on acceleration. It may also cause the on-board computer to illuminate the "Check Engine" light and set a problem code that a dealer service department can read with a diagnostic scanner tool. This process should only be undertaken by someone with solid automotive experience and knowledge.

Skill level:
Challenging

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Things you need

  • Breaker bar and socket
  • Voltmeter
  • Oscilloscope or graphing multimeter

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Instructions

    Hall Effect and Magnetoresistive Sensors

  1. 1

    Turn the ignition on but do not start the engine. Raise the hood and locate the camshaft position sensor attached to the engine block.

  2. 2

    Back-probe the camshaft sensor's electrical terminal by inserting a straight pin, T-pin or meter probe into the back of the electrical connection marked SIG; push the pin in until it contacts the internal wire. Repeat this procedure on the terminal marked GND; do not allow the pins to touch. Place the positive (red) probe of a voltmeter onto the pin marked SIG, and the negative (black) probe to the pin marked GND.

  3. 3

    Have an assistant attach a breaker bar and socket to the nut that secures the crankshaft pulley to the engine block and slowly crank the engine by turning the breaker bar clockwise by hand.

  4. 4

    Take a reading as the engine is cranked. The voltmeter should show a pulsing voltage from 0 to 5.0 volts. If the voltage remains at zero without pulsing the sensor is not receiving an electrical input from the on-board computer. If the voltage remains at a steady 5.0 volts without pulsing, most likely the sensor is malfunctioning.

    Magnetic Sensors

  1. 1

    Turn the ignition on but do not start the engine.

  2. 2

    Back-probe the sensor's electrical connection as described in Section 1, Step 2 above. Place the positive (red) probe of an oscilloscope or graphing multimeter onto the pin marked SIG, and the negative (black) probe to the pin marked GND.

  3. 3

    Have an assistant attach a breaker bar and socket to the front of the crankshaft pulley as described in Section 1, Step 3 and slowly crank the engine clockwise by hand.

  4. 4

    Take a reading. The oscilloscope or graphing multimeter should show a sign or rounded wave form with a minimum of 2.0 volts peak-to-peak. A voltage signal lower than this indicates the sensor is most likely malfunctioning.

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