How To Test The Camshaft Position Sensor (1996-1997 3.9L V6 Dodge Ram Pickup)

If you suspect that the camshaft position (CMP) sensor, on your 1996-1997 3.9L Dodge Ram pickup, is bad and causing a no-start problem or a trouble code P0340, then this is the tutorial you need to test it.

The cool thing is that the camshaft position sensor can be diagnosed as good or bad in 3 tests and they're not difficult to perform.

In this tutorial, I'll explain these 3 tests in a step-by-step manner so that you can find out if the CMP sensor is bad (or not).

NOTE: The camshaft position sensor is also known as the distributor pickup coil.

ES You can find this tutorial in Spanish here: Cómo Probar El Sensor CMP (1996-1997 3.9L Dodge Ram Pickup) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles since they use the exact same camshaft position (CMP) sensor:

• 3.9L V6 Dodge Ram 1500 Pickup: 1996, 1997.
• 3.9L V6 Dodge Ram 2500 Pickup: 1996, 1997.

WIRING DIAGRAM: You can find the ignition system wiring diagram here:

• Ignition System Wiring Diagram (1996-1997 3.9L V6 Dodge Ram Pickup).

OTHER CMP SENSOR TESTS:

• How To Test The Distributor Pickup Coil (1989-1991 3.9L V6 Dodge Ram Pickup).
• How To Test The Camshaft Position Sensor (1992-1995 3.9L V6 Dodge Ram Pickup).
• How To Test The Camshaft Position Sensor (1998-2001 3.9L V6 Dodge Ram Pickup).

IGNITION COIL TESTS:

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

Symptoms Of A Bad Camshaft Position (CMP) Sensor

Since the computer constantly monitors the CMP signal (as the engine cranks and runs), when the CMP sensor fails, you'll see the following trouble code stored in its memory:

• P0340: No Camshaft Signal At PCM.
• P1391: Intermittent Loss of CMP or CKP Signal.

These are some of the most common signs that your CMP sensor has failed:

• Engine no-start: The starter turns the engine over, but it doesn't start.
• Unexpected stalling: The engine might run fine, then suddenly die —especially while idling or driving at low speeds. No warning, no sputter, just off.
• Check Engine Light (CEL) comes on: If the PCM senses missing or unstable signals from the CMP sensor, it'll light up the CEL and set a CMP sensor trouble code (P0340 or P1391).
• Misfires or shaky idle: A weak or erratic signal messes with spark and fuel timing. That can cause misfiring, rough idle, or jerky throttle response when under load.
• Hard start (hot or cold): Starting the engine's a challenge —it starts only after several long cranks.
• Sluggish acceleration: If fuel injection isn't properly timed, the engine won't respond smoothly when you step on the gas. Acceleration feels delayed or flat.

What the CMP Sensor Does

As you're probably already aware, the camshaft position sensor (CMP) is mounted inside the distributor.

The CMP sensor used to go by the name "distributor pickup coil", but even with the new name, its role hasn't changed —it still plays a key part in helping the PCM (engine computer) manage fuel injection and ignition timing.

Here's a breakdown of what the CMP sensor does:

• Sends the Fuel Sync Signal:
  • As the engine turns, the CMP sensor generates a digital signal known as the fuel sync signal.
  • This signal tells the PCM which cylinder is on its compression stroke.
  • Without this info, the PCM can't time fuel injection properly.
• Works with the Crankshaft Position Sensor (CKP):
  • The engine also uses a CKP sensor near the flywheel to track RPM and crankshaft position.
  • But the CKP alone can't identify which stroke each cylinder is on.
  • The CMP sensor provides that missing piece, giving the PCM the reference it needs to line up fuel delivery correctly.
• Controls when injectors fire:
  • With input from the CMP, the PCM knows when to send fuel to each cylinder at the right moment in the cycle.
  • If the signal's missing or off, fuel injection becomes unstable —or it stops altogether.
• Helps with spark timing (indirectly):
  • The crankshaft sensor handles most of the spark timing, but the CMP helps the PCM figure out which cylinder is next in the firing order.

Circuit Descriptions Of The Camshaft Position Sensor

As you can see in the photo above, the camshaft position sensor is a 3-wire ignition system component. Two of these wires feed 5 Volts and Ground to the sensor (without power and Ground the sensor will not create its signal).

In the table below is a brief description of each of the 3 wires:

1996-1997 Camshaft Position Sensor Connector
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	Tan with yellow stripe (TAN/YEL)	CMP Signal

An ignition system wiring diagram, for the 1996-1997 3.9L V6 Dodge Ram 1500 pickup can be found here:

• Ignition System Wiring Diagram (1996-1997 3.9L V6 Dodge Ram Pickup).

When testing the CMP sensor, it's important to know that it creates an ON/OFF voltage signal as the engine turns. ON is when the CMP signal is at 5 Volts DC. OFF is when the CMP signal is at 0 Volts.

The cool thing is that we can see this ON/OFF voltage switching between 5 Volts and 0 Volts with a multimeter, and this is how we're gonna' test it.

Where To Buy The Camshaft Position Sensor

The camshaft position sensor (which is also called the distributor pick-up coil) is located in the distributor. It's no an expensive component and it can be found in any auto parts store, but I think you'll save a few bucks by buying it online. Check out the following links and compare:

TEST 1: Testing The Camshaft Position Signal

Generally, the camshaft position sensor will stay stuck producing a single voltage value as the engine turns when it has failed.

Thankfully, checking to see if the sensor's signal voltage is switching between 5 Volts and 0 Volts is not difficult.

In this first test section, we're gonna' tap into the tan with yellow stripe (TAN/YEL) wire, which is labeled with the number 3 in the photo above, with our multimeter.

If the sensor is working correctly, you should see the CMP signal switching between 5 Volts and 0 Volts as your helper cranks the engine.

IMPORTANT: The camshaft position sensor must remain connected to its engine harness connector for this test to work. You'll need to use a back probe or a wire piercing probe to read the CMP voltage signal within the wire. You can see an example of a wire piercing probe here (this is the one I use): Goupchn 4mm Banana to Banana Plug Test Leads Kit (Amazon affiliate link).

NOTE: Don't have a multimeter or need to upgrade yours? Check out my recommendation: Tekpower TP8268 AC/DC Auto/Manual Range Digital Multimeter (Amazon affiliate link).

These are the test steps:

1. 1

   Disconnect the ignition coil from its electrical connector. This is an important safety precaution!
   
   NOTE: Don't remove the distributor cap from the distributor. The distributor cap must be in place to hold down the camshaft position sensor.

2. 2

   Connect the black multimeter test lead directly on the battery negative (-) terminal.

3. 3

   Place your multimeter in Volts DC mode.

4. 4

   With the red multimeter test lead, probe the tan with yellow stripe (TAN/YEL) wire of the cam sensor connector.
   
   NOTE: The camshaft position sensor must remain connected to its engine wiring harness connector to be able to read its signal.

5. 5

   Have your helper crank the engine for a few seconds once the multimeter test lead connections are set up.

6. 6

   Your multimeter should see the voltage switch between 5 Volts and 0 Volts DC as the engine is cranking.

Let's examine your test result:

CASE 1: The ON/OFF voltage signal is present. This is the correct and expected test result.

Since the CMP voltage signal is switching between 5 Volts and 0 Volts, you can conclude that the CMP sensor is good and that it IS NOT behind the no-start problem.

CASE 2: The multimeter DID NOT read the indicated ON/OFF DC voltage. This test result usually means that the camshaft position sensor is defective.

Before you replace it, we need to make sure that it's getting 5 Volts on the violet with white stripe (VIO/WHT) wire. For this test go to: TEST 2: Making Sure The CMP Sensor Has 5 Volts.

TEST 2: Making Sure The CMP Sensor Has 5 Volts

As I mentioned before, the camshaft position sensor needs 5 Volts and Ground to create its ON/OFF voltage signal.

So in this test section, we're gonna' make sure that the violet with white stripe (VIO/WHT) wire is providing 5 Volts with the key on and engine off (KOEO).

If the CMP sensor is getting power from the VIO/WHT, then the next test is to make sure that it's getting Ground.

These are the test steps:

1. 1

   Disconnect the CMP sensor from its connector.

2. 5

   Connect the black multimeter test lead to the negative (-) battery terminal.

3. 2

   Place your multimeter in Volts DC mode.

4. 3

   Turn the key on but don't crank or start the engine.

5. 4

   With the red multimeter test lead, gently probe the female terminal that connects to the VIO/WHT wire.
   
   In the photo above, the VIO/WHT wire is labeled with the number 1.
   
   NOTE: This test is done on the connector that has female terminals.

6. 6

   Your multimeter should read 4.5 to 5 Volts.

Let's analyze your test result:

CASE 1: The VIO/WHT wire is providing 5 Volts to the CMP sensor. This is the correct and expected test result.

The next test is to test for the presence of Ground in the black light blue stripe wire: TEST 3: Making Sure The CMP Sensor Has Ground.

CASE 2: The VIO/WHT wire IS NOT providing 5 Volts to the CMP sensor. Without 5 Volts the camshaft position sensor will not produce a CMP voltage signal.

The most common cause of this problem is an open-circuit problem in the VIO/WHT wire between the CMP sensor's connector and the fuel injection computer's connector.

Although it's beyond the scope of this tutorial to diagnose these missing 5 Volts, your next step is to find out why it's missing and restore it.

TEST 3: Making Sure The CMP Sensor Has Ground

Up to this point, the previous two tests have confirmed that:

• The CMP sensor's voltage signal is not switching between 5 Volts and 0 Volts.
• The CMP sensor is receiving 5 Volts from the VIO/WHT wire.

Now we're gonna verify that Ground is present in the black with light blue stripe (BLK/LT BLU) wire.

I've labeled the BLK/LT BLU wire with the number 2 in the photo above.

IMPORTANT: The fuel injection computer provides Ground to the CMP sensor. Be careful and don't short the BLK/LT BLU wire to battery power (12 Volts) or you'll fry the fuel injection computer. The multimeter voltage test I'm suggesting below (for testing the presence of Ground in this wire) is a safe and accurate test.

These are the test steps:

1. 1

   Disconnect the CMP sensor from its connector.

2. 2

   Connect the red multimeter test lead to the positive (+) battery terminal.

3. 3

   Place your multimeter in Volts DC mode.

4. 4

   Turn the key on but don't crank or start the engine.

5. 5

   With the black multimeter test lead, gently probe the terminal that connects to the BLK/LT BLU wire.
   
   In the photo above, the BLK/LT BLU wire is labeled with the number 2.
   
   NOTE: This test is done on the connector that has female terminals.

6. 6

   Your multimeter should read 10 to 12 Volts DC if the BLK/LT BLU wire is providing Ground.

Let's take a look at what your test results mean:

CASE 1: Ground is present in the BLK/LT BLU wire. This is the correct test result and let's you know that the camshaft position sensor is getting Ground.

The camshaft position sensor is bad and needs to be replaced if:

• The camshaft position sensor's voltage signal is not switching ON and OFF (TEST 1).
• The VIO/WHT wire is providing the CMP sensor with 5 Volts (TEST 2).
• The BLK/LT BLU wire is providing the CMP sensor with Ground (TEST 3).

CASE 2: Ground IS NOT present in the BLK/LT BLU wire. Without Ground, the camshaft position sensor will not produce an ON/OFF voltage signal.

What's usually behind the lack of Ground is an open-circuit problem in the BLK/LT BLU wire between the CMP sensor's connector and the fuel injection computer's connector.

Although it's beyond the scope of this tutorial to check for this missing Ground, your next step is to find out why it's missing and restore it.

More 3.9L V6 Dodge Ram Pickup Tutorials

I've written quite a few 3.9L V6 Dodge ‘how to’ tutorials that may help you troubleshoot the issues on your V6 Dodge Ram pickup. You can find all in these two indexes:

• 3.9L Dodge Ram Pickup Index Of Articles.
• 3.9L, 5.2L, 5.9L Dodge Index Of Articles.

Here's a small sample of the articles/tutorials you'll find in the indexes:

• How To Test A No Start Condition (Dodge 3.9L, 5.2L, 5.9L).
• How To Diagnose Misfire Codes (Dodge 3.9L, 5.2L, 5.9L).
• How To Test The Fuel Injectors (Dodge 3.9L, 5.2L, 5.9L).
• How To Test The Ignition Coil -No Start Tests (Chrysler 3.9L, 5.2L, 5.9L).
• How To Test The MAP Sensor (P0107, P0108) (Dodge 3.9L, 5.2L, 5.9L).