You're probably ready to get this test started and over with, but, before you do...
You need to keep one very important thing in mind: When the crank sensor fails (goes BAD), the most obvious symptoms is a Cranks but Does Not Start condition due to no spark and no fuel injection.
With a BAD crank sensor on your Ford 4.6L or 5.4L vehicle you'll also see one of the following symptoms:
OK, enough reading, let's get testing!
The crank sensor on the 4.6L and 5.4L Ford engines is a two wire sensor that can be easily tested with your multimeter in AC Volts.
Remember, the battery must be fully charged for this test to produce an accurate result. Why? Well, because the strength of crank sensor's signal, that you'll be measuring with your multimeter, depends on the amount of RPMs your engine is turning as it's cranking.
The following test steps assume that you 4.6L or 5.4L pick up (car, van, or SUV) Cranks But Does Not Start (if you haven't already read the section: Symptoms of BAD Ford Crank Sensor, please do so now). OK, this is what you need to do:
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.
Reconnect the connector to the crank sensor now and place your multimeter in Volts AC mode.
Using a wire-piercing probe or another appropriate tool, probe the number 1 and number 2 wires of the crank sensor with the multimeter leads.
To see what a what wire piercing probe tool looks like, click here: Wire Piercing Probe.
It doesn't matter which multimeter lead (RED or BLACK) goes where, since the polarity of the leads doesn't matter.
When everything has been set up and you're a safe distance from the engine, have your helper crank the engine as you observe the multimeter's AC Volts readings.
If the CKP sensor is working correctly, the multimeter will register an an oscillating voltage between .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 .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.
If you have confirmed that the crank sensor is OK but your Ford still doesn't start, take a look at the following tutorial for more testing suggestions:
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 you Cranks but Does Not Start Condition.
If you'd like to buy the factory original Motorcraft crank sensor (and save), check out the section: Where to Buy the Crank Sensor and Save.
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