CKP TEST 2: The Power Circuit
The CKP sensor on your Jeep SUV needs an external power source to start creating its magic (the crank signal). Without power, well you know what will happen.
In this test step, you're gonna' verify that the crank sensor is getting power. This power is in the form of 8 Volts or 5 Volts depending on the year of your 4.0L Jeep Grand Cherokee.
NOTE: The 1996 4.0L Jeep Grand Cherokee's crank sensor's power supply is 5 Volts DC. All others are fed 8 Volts DC.
These are the test steps:
- 1
Place your multimeter in Volts DC mode.
- 2
Disconnect the crankshaft position sensor from its connector.
- 3
With the red multimeter test lead, gently probe the terminal that connects to the wire identified with the number 3 in the photo above.
On the Grand Cherokee, this is a white with black stripe (WHT/BLK) wire. On the Jeep Wrangler, this is an orange (ORG) wire. - 4
Connect the black multimeter test lead to the battery negative (-) terminal.
- 5
When everything is set up, turn the key to the ON position. No need to crank the engine with the starter motor.
- 6
your multimeter should register 4.5 to 5 (7.5 to 8) Volts DC.
OK, let's interpret the multimeter test results you just obtained. Choose from the CASES below that best match your specific results:
CASE 1: The multimeter registered 5 Volts DC when the key was turned ON. This let's you know that the CKP sensor is being fed with power from the PCM. There is still one more test to do, before we can condemn the crank sensor as bad, and that is to test the Ground circuit. Go to: CKP TEST 3: Verifying Ground.
CASE 2: The multimeter DID NOT register 5 Volts DC when the key was turned ON. Recheck your connections and try the test again.
If the multimeter still does not register 5 Volts, then you now have confirmed that the lack of power is the reason why the crank sensor is not working (and so replacing it will not help solve the problem).
Although it's beyond the scope of this article to find the cause of this lack of power (to the crank sensor), solving the issue that is causing these missing 5 Volts will solve the no-start condition of your 4.0L Jeep equipped SUV.
CKP TEST 3: Verifying Ground
In this test step, you're going to verify that the crankshaft position sensor is getting Ground. As mentioned earlier, the Ground path is completed inside the PCM.
IMPORTANT: You got to be very careful not to short this wire to battery voltage, or you run the risk of damaging the PCM. Also, do not use a test light to verify this voltage. Use a multimeter.
Alright, this is what you'll need to do:
- 1
Place your multimeter in Volts DC mode.
- 2
Disconnect the crankshaft position sensor from its connector.
- 3
With the black multimeter test lead, gently probe the terminal that connects to the wire identified with the number 2 in the photo above.
On all vehicles (Grand Cherokee and Wrangler), this is a black with light blue (BLK/LT BLU) stripe wire. - 4
Connect the red multimeter test lead to the battery positive (-) terminal.
- 5
Have you helper turn the key to the ON position. No need to crank the engine with the starter motor.
- 6
Your multimeter should register 10 to 12 Volts DC.
Choose from the CASES below that best match your specific results:
CASE 1: The multimeter registered 10 to 12 Volts DC when the key was turned ON. This is the correct and expected test result and it confirms that the CKP sensor is getting a good Ground.
This results confirms that the crankshaft position (CKP) sensor is bad and needs to be replaced only if you have:
- Confirmed in TEST 1 that the CKP sensor is not creating its ON/OFF 5 Volt signal.
- Confirmed in TEST 2 that the CKP sensor is being fed with power (5 Volts).
- In this test step, you have confirmed that it's getting Ground.
CASE 2: The multimeter DID NOT register 10 to 12 Volts DC when the key was turned ON. Recheck your connections and try the test again.
If the multimeter still does not register 10 to 12 Volts, then this result lets you know that the CKP does not have a good sensor Ground. You have now eliminated the crank sensor as the cause of the no-start condition, since without this Ground, the CKP sensor will not work.
More 4.0L Jeep Diagnostic Tutorials
You'll find all of the 4.0L Jeep “how to test” tutorials here: 4.0L Index Of Articles.
Here's a small sample of the tutorials you'll find in the Jeep 4.0L Index of Articles:
- Jeep PWM Fan Relay Test Troubleshooting An Overheating Condition.
- How To Troubleshoot A Bad Fuel Injector (Jeep 4.0L).
- How To Test For A Blown Head Gasket (Jeep 4.0L).
If this info saved the day, buy me a beer!
