CKP TEST 1: Verifying The CKP Signal

How To Test The Crank Sensor (Ford 3.0L, 3.8L)

Since the crank sensor on your Ford vehicle is a 2 wire type sensor, it can be easily tested with your multimeter set to AC Volts mode.

Just a friendly reminder: the battery should be fully charged so that you can crank the engine for several seconds while you observe your multimeter.

One last thing before we start: If your Ford vehicle has spark coming out of at least one spark plug wire, this tells you that the crank sensor is producing a signal and functioning correctly. For more info on this, take a look at the section: Symptoms Of Bad Ford Crank Sensor.

OK, this is what you need to do:

  1. 1

    After jacking up the vehicle (and placing it on jack stands) and gaining access to the crank sensor.

    Disconnect the crank sensor's electrical connector and remove some of the plastic wire loom protector and/or the black electrical tape that shields/protects the two wires of the CKP sensor.

  2. 2

    Using a wire-piercing probe or another appropriate tool, probe the number 1 and number 2 wires of the crank sensor with the multimeter test leads.

    To see what a what wire piercing probe tool looks like, click here: Wire Piercing Probe.

    It doesn't matter which multimeter test lead (RED or BLACK) goes where, since the polarity of the leads doesn't matter.

  3. 3

    Reconnect the connector to the crank sensor now and turn the multimeter's dial to Volts AC.

  4. 4

    Make sure your multimeter test leads will not interfere with the crank pulley or the serpentine drive belt.

    When all is ready and you're a safe distance from the engine, have your helper crank the engine (as you observe the multimeter).

  5. 5

    If the CKP sensor is working correctly, the multimeter will register an an oscillating voltage between 0.5 to 1 Volt AC.

    Now, to be a bit more specific: your multimeter will not register a steady AC voltage. Instead, the reading will jump between 0.5 Volts AC to 1 Volt AC continually as the engine is cranking and only when the engine is cranking.

Alright, let's find out if you have a bad CKP sensor on your hands or not. Choose from the CASES below that best match your specific results:

CASE 1: The multimeter registered the indicated AC voltage with the engine cranking. This result indicates that the CKP sensor is creating a good CKP signal and is working fine.

CASE 2: The multimeter DID NOT register the indicated AC voltage with the engine cranking. This confirms that the crank sensor is fried and is the cause of your 'cranks but does not start' condition.

The Ford manual states that A/C voltage the crank sensor must produce has to be over 0.4 Volts AC and if the voltage is not above this threshold, it's a good idea to check the resistance of the crank sensor, which should be between 300 to 800 Ohms.

Related Articles

Here, at troubleshootmyvehicle.com, there are several more 3.0L or 3.8L tutorials that you can read at: Ford 3.0L, 3.8L Index Of Articles.

At easyautodiagnostics.com (the other site I write for) you can find the following:

  1. How To Test Coil Packs.
  2. MAF Sensor Test.
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Ford Vehicles:

  • Aerostar 4.0L
    • 1995
  • Ranger 3.0L, 4.0L
    • 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008
  • Taurus 3.0L
    • 1996, 1997, 1998, 1999

Ford Vehicles:

  • Windstar 3.0L, 3.8L
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003

Mazda Vehicles:

  • B3000 3.0L
    • 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007

Mercury Vehicles:

  • Sable
    • 2003, 2004, 2005