TEST 2: Verifying The Crank Sensor Is Getting Power
Depending on what specific 3.9L, 5.2L or 5.9L Dodge pick up (van or SUV) you drive, the crank sensor will get power on a PPL/WHT (purple/white) or an ORG (orange) wire of its harness connector.
What you'll do in this test section is see if power, in the form of 5 Volts DC, is present in this PPL/WHT (or ORG) wire.
Like the previous test, this is also a simple multimeter test done with the multimeter in Volts DC mode.
NOTE: This test is done with the engine off. So, as a safety precaution don't crank or start the engine to check for this voltage.
This is what you need to do:
With your multimeter in Volts DC mode, probe the PPL/WHT (or ORG) wire of the crank sensor's harness connector.
This is the wire that connects to terminal number 3 of the harness connector shown in the illustration above.
NOTE: Do not probe the front of the crank sensor connector to verify this voltage. Back probe the connector or pierce the wire with an appropriate tool.
Ground the black lead of the multimeter to a good Ground point on the engine.
Turn the key to the on position, no need to crank the engine with the starter motor.
Your multimeter should register 4.5 to 5 Volts DC, if all is good and the PCM is feeding power to this circuit.
Let's take a look at your test results:
CASE 1: The multimeter registered 5 Volts DC when the key was turned On. This is the correct and expected test result and confirms that the crank sensor is getting power from the PCM.
The next step is to make sure that the crank sensor is getting Ground. For this test go to: TEST 3: Verifying The Crank Sensor Is Getting Ground.
CASE 2: The multimeter DID NOT register 5 Volts DC when the key was turned On. Double check that you're testing the correct wire and repeat the test.
If the multimeter still does not show 5 Volts, then this test result confirms 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 3.9L, 5.2L, or 5.9L equipped Dodge pickup (van or SUV).
TEST 3: Verifying The Crank Sensor Is Getting Ground
Up this point, you have checked and verified that the crank sensor:
One: Is not producing an on/off voltage signal (TEST 1).
Two: Verified that the PPL/WHT wire of the harness connector is feeding the crank sensor with 5 Volts DC (TEST 2).
The last test, to find out if the crank sensor is bad, is to check that it's getting Ground with a simple multimeter voltage test.
IMPORTANT: The crank sensor gets this Ground from the PCM and not chassis Ground. Be careful and don't short this wire to battery voltage or you will fry the PCM.
Alright, this is what you'll need to do:
Place your multimeter in Volts DC mode and with the black multimeter test lead, probe the BLK/LT BLU (black/light blue) wire of the crank sensor's engine wiring harness connector.
NOTE: Do not probe the front of the crank sensor connector to check this Ground. Back probe the connector or pierce the wire with an appropriate tool.
Connect the red lead of your multimeter to the battery positive terminal.
When everything is set up, have your helper turn the key to the On position.
If Ground is being fed to the crank sensor on this wire, your multimeter should register battery voltage (12+ Volts).
Let's interpret your specific test results:
CASE 1: The multimeter registered 12 Volts DC when the key was turned On. This test result tells you that the BLK/LT BLU wire is feeding the crank sensor with ground. Taking into account the results from the previous 2 tests (and this one), you can conclude that the crank sensor is bad and needs to be replaced.
Here's why: A good working crank sensor, when it receives power and Ground and the engine is cranking, will generate an On/Off 5 Volt Signal. Now, in your particular case:
- In TEST 1 you verified the crank sensor is not creating its ON/OFF 5 Volt Signal.
- In TEST 2 you confirmed that it's being fed with power (5 Volts) and in this test step, you have verified that it's getting a good ground
- ... therefore the crank sensor is bad and replacing the crank sensor will solve the cranks but does not start issue.
CASE 2: The multimeter DID NOT register 12 Volts DC when the key was turned On. Recheck your connections and try the test again.
If the multimeter still does not register 12 Volts, then this result let's you know that the BLK/LT BLU wire is not feeding the crank sensor with ground. You have now eliminated the crank sensor as the cause of the no start condition, since without this Ground, the crank sensor will not work.