The Basics Of Crank And Cam Sensors And How To Test Them

  • By: Abraham Torres-Arredondo
  • Created: 01 May 2011
  • Updated: 24 March 2024
  • Articl Id: 20
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What Are The Actual Testing Steps

Testing a CKP sensor isn't hard and the diagnostic flow is pretty straightforward. The following testing path applies to a 'cranks but does not start' condition. Although the following tests only apply to a crankshaft position sensor that has failed completely, with some modification you can also follow the same diagnostic path in diagnosing a CMP sensor.

  1. Step One.
    • Make certain that the battery is in a fully charged condition.
    • Test for spark.
      • You'll need to test for spark at all cylinders to ascertain that there's no spark present at all.
      • If spark is present, the crankshaft position sensor is working properly.
    • Test for fuel injector pulse, although depending on the fuel system design this is not always possible.
      • If the fuel injector pulse is present, the crankshaft position sensor is working properly.
  1. Step two.
    • Find the location of the crankshaft position sensor.
    • Determine type of CKP sensor (either a two or three wire type).
  2. Step three.
    • On three wire type CKP sensors:
      • Determine which wire is the power circuit.
      • Determine which wire is the Ground circuit.
      • Determine which wire is the signal wire.
    • On two wire type CKP sensors:
      • You don't have to determine which wire is which since you don't have to test for a power supply. Also, the multimeter's leads are hooked up to both wires at the same time to read the signal the sensor produces.
  3. Step four.
    • On three wire type CKP sensors:
      • Probe the power circuit to verify the presence of the specified voltage. This voltage is usually verified with the key on or engine cranking.
      • Probe the Ground circuit to verify that Ground does exist. This Ground is usually verified with the key on or engine cranking.
      • Probe the signal wire. The presence of this signal can only be verified with the engine cranking and with the multimeter in Hertz (Hz) frequency mode or in Volts DC mode.
    • On two wire type CKP sensors:
      • Probe both wires coming out of the sensor with both leads of your multimeter. The polarity of the leads doesn't matter. In other words, the red and black lead can go to any of the two wires.
      • The presence of this signal can only be verified with the engine cranking and with the multimeter in Volts AC.
  4. Step Five.
    • If no signal is present:
      • The crankshaft position sensor is bad, replace it.
    • If a signal is present:
      • The crankshaft position sensor is good.

As always, things on paper always seem easier than in their actual application and this is sometimes true when you're testing CKP and CMP sensors. For example, in some cars and trucks, it's next to impossible to verify the fuel injector pulses with a fuel injector Noid light. Why? Well because the engineers have located them inside or underneath the intake manifold plenum. Don't let this deter you, it's just a matter of skipping this test and going on with the rest.

Once you overcome these obstacles, you'll find that testing them is not that hard. The one thing I recommend you do, is to practice on a good working car to see how all of this works. Well, in closing, if you found this article helpful -please tell a friend!!!

Related Crankshaft Position Test Articles

Below you'll find a list of test tutorials that will show you how to test the crankshaft position sensor for several different types of makes:

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