The crankshaft position (CKP) sensor is a two-wire variable reluctance sensor that you can easily test with a multimeter.
In this tutorial, I'll explain the test in a step-by-step manner. With your test results, you'll easily and quickly find out if the CKP sensor is good or bad.
NOTE: You can find the 1991-1997 4.0L Ford Explorer (Aerostar) CKP sensor test tutorial here:
Contents of this tutorial:
APPLIES TO: This tutorial applies to the following vehicles:
- 4.0L OHV V6 Ford Explorer: 1997, 1998, 1999, 2000, 2002, 2003, 2004, 2005.
- 4.0L SOHC V6 Ford Explorer: 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010.
- 4.0L V6 SOHC Mercury Mountaineer: 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010.
OHV: Over Head Valve.
SOHC: Single Over Head Camshaft.
Important Tips And Suggestions
TIP 1: The CKP sensor is located right behind the crankshaft pulley, since the CKP sensor's reluctor wheel is behind (and part of) the crankshaft pulley.
TIP 2: The battery in your 4.0L Ford Explorer (Mercury Mountaineer) must be fully charged. This is important because you'll be measuring the CKP sensor's signal while the engine is cranking. A low battery will cause the engine to crank slower than normal and you're not gonna' see a good CKP sensor signal result on your multimeter.
TIP 3: You'll need to jack up the vehicle to gain access to the CKP sensor. Use a jack stand to hold the car up in the air. Do not trust the jack! Use safety glasses also. Think safety all of the time!
TIP 4: The first thing you should do, before testing the CKP sensor is checking for spark at all six spark plug wires (high tension cables). Why? Well if even just one spark plug cable has spark, this tells you that the CKP sensor is OK.
In other words, when the crankshaft position sensor goes bad, you'll get a no-spark no-start condition. So, if you're getting spark, even if in just one cylinder, the CKP sensor is good and this test will not help you.
TIP 5: This tutorial does not cover any remove and replace instruction for accessing or replacing the CKP sensor. You'll need a repair manual for them (or Google).
Symptoms Of A Bad CKP Sensor
The crankshaft position sensor usually fails in one of two ways:
- Complete failure. In this case the sensor stops functioning.
- Intermittent failure. The sensor functions most of the time, but now and then it won't.
When the CKP sensor suffers a complete failure, the engine will crank but won't start.
When the CKP sensor can fails intermittently, the engine starts and runs most of time but now and then it won't.
Where To Buy The CKP Sensor And Save
The following links will help you comparison shop for the CKP sensor of known automotive brands (no knockoffs):
Not sure if the CKP sensor fits your particular 4.0L Ford Explorer or Mercury Mountaineer? Don't worry, once you get to the site they'll make sure it fits by asking you the specifics of your particular Ford vehicle. If it doesn't fit, they'll find you the right CKP sensor.
Testing The CKP Sensor Signal With A Multimeter
As I mentioned at the beginning of this tutorial, the CKP sensor is a two-wire type sensor. This means you can easily test its output signal with a multimeter.
To access the CKP sensor, you'll have to jack up the vehicle (and place it on jack stands).
The following test instructions assume you have already done all of this leg work.
IMPORTANT: This test is done with the CKP sensor connected to its electrical connector.
OK, these are the test steps:
- 1
Unplug the CKP sensor from its electrical connector.
You may need to 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
Connect the red multimeter test lead to one of the two wires of the connector.
IMPORTANT: Make sure your multimeter test leads DO NOT interfere with the crankshaft pulley or the serpentine drive belt, since you'll be cranking the engine in one of the following steps. - 3
Connect the black multimeter test lead to the remaining wire of the connector
IMPORTANT: Make sure your multimeter test leads DO NOT interfere with the crankshaft pulley or the serpentine drive belt, since you'll be cranking the engine in one of the following steps. - 4
Reconnect the connector to the CKP sensor.
- 5
Turn the multimeter's dial to Volts AC.
- 6
Have your helper crank the engine when the test is set up and you're standing a safe distance from the engine.
- 7
Your multimeter should register an AC voltage between 0.5 to 1.2 Volts AC while the engine is cranking.
When the engine is not cranking, you should see 0 Volts AC.
NOTE: Your multimeter will not register a steady AC voltage. Instead, the reading will fluctuate between 0.5 to 1.2 Volts AC continually as the engine is cranking and only when the engine is cranking.
OK, let's take a look at what your test results mean:
CASE 1: The multimeter registered the indicated AC voltage with the engine cranking. This test result indicates that the CKP sensor is good.
Since the engine is not starting, 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 test result confirms that the CKP sensor is fried. Replace the crankshaft position sensor.
More 4.0L Ford Explorer And Mercury Mountaineer Tutorials
You can find more 4.0L V6 Ford Explorer and Mercury Mountaineer diagnostic tutorials here:
Here's a sample of the tutorials you'll find in the index:
- How To Test For A Blown Head Gasket (Ford 4.0L Explorer, Aerostar And Mercury Mountaineer).
- How To Test The Fuel Pump (Ford 4.0L Explorer, Aerostar And Mercury Mountaineer).
- How To Test Engine Compression (1991-2010 4.0L Ford Explorer, Aerostar, And Mercury Mountaineer).
If this info saved the day, buy me a beer!
