How To Test The Crankshaft Position Sensor (1998-2001 3.9L V6 Dodge Ram Pickup)

The crankshaft position (CKP) sensor sits right on the transmission bell housing, and the good news is —it's not hard to test.

Since the CKP sensor is a 3-wire Hall-Effect type, it can easily be checked with a regular multimeter -no need for a scan tool or any other expensive testing equipment!

In this tutorial, I'll walk you through each test step-by-step. By the end of your tests, you'll know for sure if the CKP sensor's dead and behind your Dodge Ram's no-start issue.

ES You can find this tutorial in Spanish here: Cómo Probar El Sensor De Posición Del Cigüeñal —CKP (1998-2001 3.9L V6 Dodge Ram Pickup) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles:

• 3.9L V6 Dodge Ram 1500 Pickup: 1998, 1999, 2000, 2001.
• 3.9L V6 Dodge Ram 2500 Pickup: 1998, 1999, 2000, 2001.

WIRING DIAGRAMS:

• Ignition System Wiring Diagram (1998-2000 3.9L V6 Dodge Ram Pickup).
• Ignition System Wiring Diagram (2001 3.9L V6 Dodge Ram Pickup).

IGNITION SYSTEM TESTS:

• How To Test The Ignition Coil (1992-2001 3.9L V6 Dodge Ram Pickup).
• How To Test The Camshaft Position Sensor (1998-2001 3.9L V6 Dodge Ram Pickup).

Important Tips And Suggestions

TIP 1 → On-Car Test: We're gonna test the CKP sensor while it's still bolted onto the bell housing. It's important that you don't remove it (to test it).

TIP 2 → Turn the engine by hand (not using the starter): The only way to get a clean, reliable voltage reading on your multimeter is by slowly cranking the engine by hand.

This part really matters —if you crank the engine using the starter, you won't be able to see the CKP signal voltage pulses with your multimeter.

By "turning it by hand", I mean grabbing a 1/2-inch ratchet and the correct socket so you can manually rotate the crankshaft pulley.

TIP 3 → Always test for spark first: If you already checked for spark and the ignition coil is sparking away, that means the CKP sensor's working.

If you haven't checked for spark, this tutorial will help you:

• How To Test The Ignition Coil (1992-2001 3.9L V6 Dodge Ram Pickup).

How The CKP Sensor Works

The crankshaft position sensor (CKP) is mounted right on the bell housing of the transmission. From that spot, it watches the flywheel's notches (slots) as the engine turns over or runs. Let's break it down a little more:

• CKP signal: The flywheel has 6 notch groups arranged evenly around its outer edge —3 single-notch sets and 3 double-notch sets. As each group moves past the CKP sensor, it sends a signal to the computer:
  • Each single notch produces one pulse.
  • Each double notch (a pair of notches close together) creates two back-to-back pulses.
  All together, the sensor sends 9 pulses per full crankshaft revolution —3 from the single notches and 6 from the doubles— which the engine computer uses to keep everything timed correctly.
• Purpose: These pulses help the engine control module figure out the crankshaft's exact position and RPM. That info gets combined with the camshaft sensor (CMP) data to precisely time ignition and fuel delivery.
• No CKP signal, no-start: If the CKP signal doesn't reach the computer, it shuts off the Auto Shutdown (ASD) relay and the fuel pump relay. That cuts off power to both the ignition coil and injectors —and the engine won't start.
• ON/OFF voltage: As the crankshaft spins, the CKP sensor flips between ON and OFF states. You'll see 5 Volts DC when it's ON and 0 Volts when it's OFF.
  • A single-notch set causes one clean voltage change.
  • A double-notch set causes two quick voltage flips, one after the other.
• Testing: Here's the good part —you can actually watch these voltage changes happen using an ordinary multimeter (if you turn the engine over manually). That's exactly what we'll be doing in the test steps.

CKP Sensor Connector Pinout

Pin	Wire Color	Description
1	Violet with white stripe (VIO/WHT)	5 Volts DC
2	Black with light blue stripe (BLK/LT BLU)	Sensor Ground
3	Grey with black stripe (GRY/BLK)	CKP Signal

Where To Buy The CKP Sensor And Save

If you're unsure whether the CKP sensor above fits your exact vehicle, don't worry. When you get to the site, they'll double-check the fit for you by asking for your Dodge Ram pickup's details. If it doesn't fit, they'll help you get the right one.

TEST 1: Checking The CKP Signal With A Multimeter

To our CKP sensor diagnostic under way, we're gonna see if it's actually putting out an ON/OFF signal through its signal wire.

The CKP signal wire is the gray with black stripe (GRY/BLK) wire coming out of the CKP sensor's engine wiring harness connector.

Since the sensor has to stay plugged in for this test to work, you'll need to tap into that GRY/BLK wire directly.

There are two ways to do it:

• You can either back-probe the connector.
• Or use a wire-piercing tool.

Here's a closer look at wiring piercing probe and where to get it: Goupchn 4mm Banana to Banana Plug Test Leads Kit, 15PCS Five Colors (Amazon affiliate link).

IMPORTANT: Like I said earlier, don't remove the CKP sensor for this test. If you pull the sensor out and reinstall it, the sensor's air gap calibration will be lost and the flywheel's reluctor ring will smack right into it and destroy it.

NOTE: Need to buy a multimeter or an upgrade? This is the one I have and use: Tekpower TP8268 AC/DC Auto/Manual Range Digital Multimeter (Amazon affiliate link).

Alright, let's get started:

1. 1

   Disconnect the ignition coil from its harness connector. This is a crucial safety step —don't skip it before moving forward.

2. 2

   Set your multimeter to DC Volts mode.

3. 3

   Clip the black multimeter lead to the battery's negative (-) terminal.

4. 4

   Turn the key to the ON position (but don't start the engine). This powers up the CKP sensor and gets it ready for testing.

5. 5

   Find the CKP sensor connector.
   
   Once you've located it, peel off any wire loom or tape that's covering the sensor wires. You only need enough space to tap into the wire for the CKP signal test.
   
   NOTE: Double-check that you're working with the right connector. The CKP and CMP sensor connectors are almost identical. The one you need goes to the sensor mounted on the transmission bell housing —not the one inside the distributor.

6. 6

   Connect the red multimeter lead to the GRY/BLK wire on the CKP harness connector.
   
   That's the wire going to terminal number 3 —just like the diagram shows above.
   
   NOTE: You've gotta leave the CKP sensor plugged in while running this test.

7. 7

   Have someone slowly turn the crankshaft pulley by hand (clockwise) while you keep an eye on the meter.
   
   NOTE: Only use hand-cranking here —the starter motor will turn the engine over too fast and you're not gonna be able to see the ON/OFF voltage changes.

8. 8

   Watch for the voltage to toggle between 0 and 5 Volts DC as the crank pulley turns.
   
   OFF means 0 Volts. ON means 5 Volts. Have your helper turn the crank nice and steady so you can catch the voltage changes.
   
   NOTE: You should catch a total of 6 sets of voltage flips for each full rotation of the crankshaft: 3 single flips and 3 double flips.
   
   → A single flip happens when a single notch on the flywheel passes under the sensor and you'll see the voltage jump once (from 0 to 5 or vice versa).
   → A double flip happens when a pair of notches (double notch set) passes by —you'll see the voltage flip twice in quick succession.

Now let's break down what your results tell you:

CASE 1: You saw the multimeter switch back and forth between ON and OFF (5V and 0V). That's exactly what you want —your CKP sensor's working like it should.

Since the sensor's fine, you'll need to keep digging for the real cause of the engine's no-start problem. Your next move should be to test the CMP sensor:

• How To Test The Camshaft Position Sensor (1998-2001 3.9L V6 Dodge Ram Pickup).

CASE 2: You didn't see the multimeter change at all while turning the crank by hand. That tells you the CKP sensor isn't sending a signal —and the PCM needs that signal to fire spark and inject fuel.

In most cases, this means the CKP sensor has failed. Replacing it usually solves the problem and gets the engine going again.

Before throwing in a new one, make sure the sensor's actually getting its power supply (5 Volts from the PCM). Your next test is here: TEST 2: Making Sure The CKP Sensor Has Power.

TEST 2: Making Sure The CKP Sensor Has Power

The crankshaft position (CKP) sensor needs both power and Ground to do its job (it's a Hall-Effect type sensor). So in this part of the test, you'll use your multimeter and check if the sensor's actually getting power.

That power comes in as a 5 Volt DC signal, sent from the PCM when the key's turned to the ON position —and also while the engine's cranking or running.

It's the purple with white stripe (PPL/WHT) wire that delivers those 5 Volts to the CKP sensor.

Here's how to run this test:

1. 1

   Unplug the CKP sensor from the engine harness.

2. 2

   Set the multimeter to Volts DC.

3. 3

   Connect the black lead of your multimeter to the battery's negative (-) terminal.

4. 4

   Turn the ignition key to the ON position. You don't need to start or crank the engine.

5. 5

   Touch the red multimeter lead to terminal 1 of the harness connector.
   
   Check that the terminal actually connects to the PPL/WHT wire (PPL/WHT = VIO/WHT).
   
   NOTE: You're testing the engine wiring harness connector —the one with the female terminals.

6. 6

   Your meter should read between 4.5 and 5 Volts DC if the PCM is delivering power like it's supposed to.

Now, here's what those results tell you:

CASE 1: You're reading 4.5 to 5 Volts DC. That confirms the PCM is sending power to the CKP sensor like it should.

The next step is to check for a good Ground. Head here for that: TEST 3: Making Sure The CKP Sensor Has Ground.

CASE 2: You're not seeing 4.5 to 5 Volts DC. Go back and recheck your connections, then run the test one more time to rule out a bad contact.

If you still don't get 5 Volts, there's your issue: the CKP sensor isn't the root of the problem —it's just not being powered. Replacing the sensor won't do anything. You've got fix that power issue.

Figuring out why the power's missing is beyond this guide, but once you solve it, your V6 Dodge Ram pickup should fire right up again.

TEST 3: Making Sure The CKP Sensor Has Ground

Up to this point, your CKP sensor tests have confirmed two things:

• TEST 1: The CKP sensor isn't generating an ON/OFF voltage signal.
• TEST 2: The sensor is getting a steady 5 Volts DC.

Now it's time for the final check —you're gonna make sure the sensor has a solid Ground with a quick multimeter voltage test.

The Ground for the CKP sensor comes through the black with light blue stripe (BLK/LT BLU) wire, which runs straight from the PCM (the engine's fuel injection computer).

IMPORTANT: That BLK/LT BLU wire is connected directly to the PCM —if you connect it to battery voltage, you'll fry the computer. So take care. The test method below is a safe way to check for Ground in this circuit.

Here's what you need to do next:

1. 1

   Unplug the CKP sensor from the engine harness.

2. 2

   Set your multimeter to Volts DC mode.

3. 3

   Connect the red lead of your multimeter to the battery's positive (+) terminal.

4. 4

   Turn the key to the ON position. You don't need to start or crank the engine.

5. 5

   Touch the black multimeter lead to terminal number 2 on the CKP connector.
   
   Make sure you're probing the terminal linked to the BLK/LT BLU wire.

6. 6

   If Ground is present, your multimeter should read somewhere between 10 and 12 Volts DC.

Let's interpret the results:

CASE 1: You're reading between 10 and 12 Volts DC. That tells you the BLK/LT BLU wire is delivering a good Ground to the CKP sensor.

If you've confirmed all three test steps:

• TEST 1: The CKP sensor isn't sending out its ON/OFF 5V signal.
• TEST 2: It's getting 4.5 to 5 Volts.
• This test: It's also receiving proper Ground.

Then it's clear that the CKP sensor has failed and needs to be replaced.

CASE 2: You didn't get a voltage reading between 10 and 12 Volts DC. Double-check your test connections and give it another go.

If the reading still doesn't show up, then the BLK/LT BLU wire isn't Grounding the sensor. So the sensor itself isn't the problem —the real issue is that missing Ground. Fixing that is your next step toward getting the engine to start again.

More 3.9L V6 Dodge Ram Pickup Tutorials

You can find a complete list of wiring diagrams and diagnostic tutorials for the V6 Dodge Ram pickup here:

• 3.9L V6 Dodge Ram Index Of Articles.

Here's a sample of the tutorials you'll find in the index:

• How To Test The TPS (1997-2001 3.9L V6 Dodge Ram Pickup).
• Testing The Front Oxygen Sensor's Performance (1996-2001 3.9L V6 Dodge Ram Pickup).
• How To Test The Fuel Pump (1992-2001 3.9L V6 Dodge Ram Pickup).
• How To Test The Intake Air Temp (IAT) Sensor (1998-2001 3.9L V6 Dodge Ram Pickup).