You can easily test the crankshaft position (CKP) sensor, which is located near the crankshaft pulley, with a multimeter. No scan tool needed. In this tutorial, I'll show you how to do it.
You'll easily and quickly find out if the CKP is good or bad on your 1991-1997 4.0L V6 Ford Explorer (Aerostar).
NOTE: You can find the 1991-1997 4.0L Ford Ranger (Mazda B4000) CKP sensor test tutorial here:
- How To Test The CKP Sensor (1991-1997 4.0L Ford Ranger And Mazda B4000) (at: easyautodiagnostics.com).
Contents of this tutorial:
APPLIES TO: This tutorial applies to the following vehicles:
- 4.0L V6 Ford Aerostar: 1991, 1992, 1993, 1994, 1995, 1996, 1997.
- 4.0L V6 Ford Explorer: 1991, 1992, 1993, 1994, 1995, 1996, 1997.
The 1997-2010 Ford Explorer (Mercury Mountaineer) CKP test tutorial is here:
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 (Aerostar) 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
In the most cases, when the crankshaft position sensor fails, your 4.0L Ford Explorer (Aerostar) will not start. To be more specific, the engine will crank but won't start.
Unfortunately, in a few cases, the CKP sensor can fail intermittently. When this happens, the CKP sensor will function most of time but every now and then it won't.
These intermittent CKP sensor failures can be frustrating, since you'll be able to start and drive the vehicle but you don't know when it'll not start.
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 Aerostar? 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
The CKP sensor test itself is pretty easy, since the sensor is a two wire type.
What is difficult is getting to it, since you'll have to jack up the vehicle (and place it on jack stands) to get to the CKP sensor.
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.
CAUTION: The engine has to be cranked to test the CKP sensor's AC voltage output. Be careful and take all necessary safety precautions.
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 interpret the multimeter test results:
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 Aerostar Tutorials
You can find more 4.0L V6 Ford Explorer and Aerostar 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!
