A bad crankshaft position (CKP) sensor will cause your 1993-1995 4.0L Jeep Cherokee to crank but not start due to a lack of spark.
In this tutorial, I'll explain how to test it and find out if it's bad or not in 3 tests.
Contents of this tutorial:
- Important Tips And Suggestions.
- Where To Buy The Crankshaft Position Sensor And Save.
- Circuit Descriptions Of The Crankshaft Position Sensor.
- TEST 1: Testing The CKP Signal With A Multimeter.
- TEST 2: Making Sure The CKP Sensor Is Getting Power.
- TEST 3: Making Sure The CKP Sensor Is Getting Ground.
- More 4.0L Jeep Cherokee Tutorials.
You can find this tutorial in Spanish here: Cómo Probar El Sensor CKP (1993-1995 4.0L Jeep Cherokee) (at: autotecnico-online.com).
APPLIES TO: This tutorial, on testing the CKP sensor, applies to the following vehicles:
- 1993, 1994, 1995 4.0L Jeep Cherokee.
RELATED WIRING DIAGRAMS:
- How To Test The Crankshaft Position Sensor (1996 4.0L Jeep Cherokee).
- How To Test The Crankshaft Position Sensor (1997-1998 4.0L Jeep Cherokee).
Important Tips And Suggestions
TIP 1: The crankshaft position sensor test I'm gonna' show you here is an on-car test. The photos in this tutorial show the CKP sensor out of the vehicle, but this is just to make it easier to explain the tests.
TIP 2: To get an accurate test result you can trust, you'll need to turn the engine by hand (manually). This is super important, because if you use the starter motor to crank the engine- you're not gonna' get an accurate result.
By turning the engine by hand, I mean turning the engine using a 1/2 ratchet wrench and an appropriate socket on the crank pulley.
TIP 3: Test the spark plug wires for spark before testing the CKP sensor (if you haven't already).
If any of the spark plug wires are sparking, then the CKP sensor is OK and doing its job.
TIP 4: Take all necessary safety precautions. Think safety all of the time.
Where To Buy The Crankshaft Position Sensor And Save
The following links will help you to comparison shop for the CKP sensor on the 1993-1995 4.0L Jeep Cherokee:
Not sure if the above crankshaft position sensor fits your particular 1993-1995 4.0L Jeep? Don't worry, once you get to the site, they'll make sure it fits by asking you the particulars of your vehicle. If it doesn't fit, they'll find you the right one.
Circuit Descriptions Of The Crankshaft Position Sensor
The crankshaft position sensor on your 4.0L Jeep Cherokee is a Hall-Effect 3-wire crankshaft position sensor.
What this means: it produces an ON/OFF DC voltage signal that can be easily measured with a multimeter, an oscilloscope, and even an LED light.
Each one of the three wires that connect to it have a specific job to do. Here's a brief description of each one:
|Black With Light Blue Stripe (BLK/LT BLU)
|Gray With Black Stripe (GRY/BLK)
You can consult the following ignition system wiring diagram for more info:
TEST 1: Testing The CKP Signal With A Multimeter
The very first thing that we're gonna' do is test the crankshaft position sensor's signal with a multimeter.
The wire that we're gonna' test is the gray with black stripe (GRY/BLK) wire of the CKP sensor's engine wiring harness connector.
NOTE: The CKP sensor must remain connected to its electrical connector for this test to work. You'll need to use a back probe on the connector or a wire piercing probe on the wire. You can see an example of this tool (and where to buy it) here: Wire Piercing Probe Review (Power Probe PWPPPPP01).
OK, let's get started:
Disable the ignition system by disconnecting the ignition coil.
This step is important do not proceed to the next step until you've done this.
Disconnect all of the fuel injectors from their electrical connectors.
This step is important also, since this will prevent the PCM from injecting fuel into the engine cylinders (if the CKP sensor is OK).
Locate the CKP sensor's connector.
Once you've located the CKP sensor connector, remove some of the plastic wire loom protector and/or the black electrical tape that shields the three wires of the CKP sensor. Remove enough of this electrical tape insulation to gain comfortable access to the three wires it protects.
Place the multimeter in Volts DC mode.
Connect the red multimeter test lead to the GRY/BLK wire of the engine wiring harness connector with an appropriate tool.
NOTE: The CKP sensor must remain connected to its connector. Use a back probe on the connector or a wire piercing probe on the wire to access the signal inside the GRY/BLK wire.
Connect the black multimeter test lead to battery negative (-) terminal.
Turn the key to the ON position (but don't crank the engine). This will power up the crankshaft position sensor.
Have a helper turn the crankshaft pulley by hand in a clock-wise direction.
Your job is to keep your eyes glued on the multimeter's display.
NOTE: Do not use the starter motor to crank the engine, since this will defeat the accuracy of this test.
Your multimeter should show an ON/OFF voltage of 5 Volts/0 Volts DC as the crankshaft pulley is turned by hand.
OFF is when your multimeter reads 0 Volts and ON is when it reads 5 Volts. The key to seeing this voltage change is to turn the crankshaft pulley slowly and steadily.
Alright, let's interpret your test results:
CASE 1: The multimeter registered the ON/OFF 5 Volts DC as the crankshaft pulley was hand-turned. This is the correct and expected test result and it tells you that the CKP sensor is working OK.
CASE 2: The multimeter DID NOT register the ON/OFF 5 Volts DC as the crankshaft pulley was hand-turned. In most cases, you can conclude the CKP sensor is fried and that it needs to be replaced. But (yeah, I know) not always.
Therefore, the next step is to check that the crankshaft position sensor is getting power. This comes in the form of 8 Volts and from your Jeep Cherokee's fuel injection computer. For this test go to: TEST 2: Making Sure The CKP Sensor Is Getting Power.