How To Test The Camshaft Position Sensor (1992-1995 3.9L V6 Dodge Ram Pickup)

Testing the camshaft position sensor, which is located inside the distributor, is not difficult at all.

The cool thing is that you don't need any expensive diagnostic equipment to do it, since it can be tested with a simple multimeter.

In this tutorial, I'll explain the 3 tests that you need to perform to find out if it's good or bad.

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

You can find this tutorial in Spanish here: Cómo Probar El Sensor CMP (1992-1995 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 150 Pickup: 1992, 1993.
• 3.9L V6 Dodge Ram 250 Pickup: 1992, 1993.
• 3.9L V6 Dodge Ram 1500 Pickup: 1994, 1995.
• 3.9L V6 Dodge Ram 2500 Pickup: 1994, 1995.

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

• Ignition System Wiring Diagram (1992-1993 3.9L V6 Dodge Ram Pickup).
• Ignition System Wiring Diagram (1994-1995 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 (1996-1997 3.9L V6 Dodge Ram Pickup).
• How To Test The Camshaft Position Sensor (1998-2001 3.9L V6 Dodge Ram Pickup).

Symptoms Of A Bad Camshaft Position (CMP) Sensor

The fuel injection computer is programmed to set a trouble code when the CMP sensor fails (but doesn't always do so). When it does set a trouble code, you'll see the following trouble code stored in the computer's memory:

• Code 11: No Crankshaft Reference Signal Detected During Cranking.
• Code 54: No Cam (Fuel) Sync Signal Detected.

Here are some other problems you might run into:

• Cranks but won't start: The engine turns over, but that's it —it doesn't fire up.
• Sudden stalling: It can run just fine for a bit, then out of nowhere, it shuts off —usually when you're idling or rolling at low speed.
• Check Engine Light (CEL) turns on: If the PCM throws a code 11 or 54, it'll light up the CEL on the dash.
• Rough idle or misfires: A glitchy sensor signal can mess up fuel delivery. That leads to misfiring, stumbling, or a rough idle.
• Hard starts (hot or cold): If the sensor's not totally dead but going bad, the engine might start —but only after several tries.
• Slow throttle response: When the CMP sensor's acting up, you'll notice lag when hitting the gas, like the engine's hesitating to respond.

What the Distributor Pick-Up Coil Does

On 1992–1995 V6 Dodge Ram pickups, the camshaft position (CMP) sensor sits inside the distributor and plays a big part in how the engine runs.

It sends a signal to the PCM (engine computer), helping it control both fuel injection and spark while the engine's cranking or running.

Here's a closer look at what the pickup coil actually does:

• Teams up with the crankshaft sensor for timing control:
  • The PCM relies on signals from both the CMP and CKP sensors to manage when to inject fuel and fire the spark.
  • The crankshaft sensor (CKP) gives the PCM engine speed, while the CMP identifies which cylinder is up for compression.
• Acts as a reference marker for the PCM:
  • As the engine spins, the CMP sensor creates a digital ON/OFF voltage signal —called the Fuel Sync signal.
  • This signal tells the PCM which cylinder is on the compression stroke, so it can time the injectors properly.
• Controls when fuel and spark happen:
  • With the CMP signal, the PCM powers up the ASD relay and the fuel pump relay.
  • It also uses the signal to fire the injectors and ignition coil at the right time.
• No CMP signal? Engine won't run:
  • If the CMP signal drops out, the PCM shuts down the ASD and fuel pump relays.
  • That cuts off power to the fuel pump, ignition coil, and fuel injectors. The engine will crank, but it won't start.

Circuit Descriptions Of The Camshaft Position Sensor

As shown in the photo above, the camshaft position sensor's electrical connector has three wires coming out of it.

The table below gives you a quick breakdown of what each of those wires does:

1992-1995 Camshaft Position Sensor Connector
Pin	Wire Color	Description
1	Orange (ORG)	8 Volts DC
2	Black with light blue stripe (BLK/LT BLU)	Sensor Ground
3	Tan with yellow stripe (TAN/YEL)	CMP Signal

The following ignition system wiring diagrams will further help you identify the camshaft position sensor circuits:

• Ignition System Wiring Diagram (1992-1993 3.9L V6 Dodge Pickup And Van).
• Ignition System Wiring Diagram (1994-1995 3.9L V6 Dodge Ram 1500 And 2500 Pickups).

In a nutshell, as the engine turns (either because it's cranking or running) the camshaft position sensor creates an ON/OFF voltage signal. ON is when the CMP signal is at 5 Volts DC. OFF is when the CMP signal is at 0 Volts.

This ON/OFF voltage can be observed easily with a multimeter in Volts DC mode, and this is how we're gonna' test it.

Where To Buy The Camshaft Position Sensor

The following links will help you comparison shop for the camshaft position sensor (distributor pickup coil). I think you'll save a few bucks:

TEST 1: Testing The Camshaft Position Signal

The very first thing that we're going to do is to make sure that the camshaft position sensor is creating and ON/OFF voltage signal when the engine is cranking.

For the most part, when the CMP sensor fails it will stay stuck producing a single voltage value as you crank the engine.

To be a bit more specific, you're not going to see the ON/OFF voltage signal on your multimeter when you crank the engine.

If your test result confirms that the camshaft position sensor is not producing its signal, then the next step is to make sure that it's getting 8 Volts.

IMPORTANT: The camshaft position sensor must be 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: Wire Piercing Probe Review (Power Probe PWPPPPP01).

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

These are the test steps:

1. 1

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

2. 2

   Place your multimeter in Volts DC mode.

3. 3

   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.

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 CMP signal test result:

CASE 1: The CMP sensor is producing an ON/OFF voltage signal. This is the correct and expected test result.

You can conclude that the camshaft position sensor is functioning correctly and IS NOT behind the problem causing the engine to not start.

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, make sure it's getting power and Ground. For the next test go to: TEST 2: Making Sure The CMP Sensor Has 8 Volts.