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

The camshaft position sensor, which sits inside the distributor, is a 3-wire Hall-Effect sensor. And let me tell you from experience —you can test it pretty easily using just a regular multimeter.

In this guide, I'm gonna walk you through the three tests you need to run on the CMP sensor to figure out if it's working right or completely shot.

NOTE: This sensor's also known as the distributor pickup coil.

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.

IGNITION SYSTEM WIRING DIAGRAMS:

• Ignition System Wiring Diagram (1992-1993 3.9L V6 Dodge Ram Van).
• Ignition System Wiring Diagram (1994 3.9L V6 Dodge Ram Van).
• Ignition System Wiring Diagram (1995 3.9L V6 Dodge Ram Van).

OTHER CMP SENSOR TESTS:

• How To Test The Distributor Pickup Coil (1989-1991 3.9L V6 Dodge Ram Van).
• How To Test The Camshaft Position Sensor (1996-1997 5.2L, 5.9L V8 Dodge Ram Van).
• How To Test The Camshaft Position Sensor (1998-2003 3.9L V6 Dodge Ram Van).

Symptoms Of A Bad Camshaft Position (CMP) Sensor

If a problem occurs with the CMP sensor, the check engine light usually kicks on (as long as the engine manages to start), and the computer logs one of these trouble codes:

• Code 11: No Crankshaft Reference Signal Picked Up While Cranking.
• Code 54: No Cam (fuel Sync) Signal Detected.

Along with that, you might run into one or more of these problems:

• Cranks but won't fire up: The engine turns, but there's either no spark or fuel. That's because the computer's not powering the injectors or ignition coil.
• Sudden engine shutdown: It could be running just fine, then suddenly cut off —especially when you're idling or starting to step on the gas.
• Check Engine Light (CEL) stays on: If the computer logs code 11 or 54, the CEL's gonna light up for sure.
• Misfiring or rough idling: A weak or choppy signal messes with fuel and spark timing. That causes hesitation, misfires, or an unsteady idle.
• Hard to start —hot or cold: If the sensor's failing but not totally gone, it might take a few tries to get the engine going.
• Sluggish throttle response: Step on the gas and there's a delay. This usually happens when the sensor is beginning to fail —but not totally dead yet.

What The CMP Sensor Actually Does

Here's what the CMP sensor (distributor pickup coil) actually does:

• Teams up with the crank sensor to handle timing:
  • The computer needs input from both the camshaft position sensor (CMP) and the crankshaft position sensor (CKP) to control spark and fuel delivery.
  • The CKP tells the computer how fast the engine's spinning, while the CMP points out which cylinder's on the compression stroke.
• Sends the Fuel Sync signal to the computer:
  • As the engine rotates, the CMP kicks out a digital ON/OFF signal —that's your Fuel Sync signal.
  • That signal tells the computer when to fire each injector right on time.
• Enables the ignition and fuel systems:
  • The computer uses the CMP signal to turn on the ASD relay and fuel pump relay.
  • That same signal also controls when the injectors pulse and when the ignition coil fires.
• No CMP signal? The whole thing shuts down:
  • When the computer doesn't see the CMP signal, it kills power to both the ASD and fuel pump relays.
  • That means no fuel pump, no ignition coil, no injectors. The engine will crank, but it ain't gonna start.

Circuit Descriptions Of The Camshaft Position Sensor

The camshaft position sensor is a 3-wire sensor. Each one has a specific job to do. Here's a brief description of what each one 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

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

While the engine's cranking or running, the camshaft position sensor sends out a voltage signal that flips between ON and OFF:

• ON: When it's ON, the signal reads 5 Volts DC.
• OFF: When it's OFF, it drops all the way down to 0 Volts.

You and I can check this ON/OFF switching pattern ourselves using a basic multimeter —and that's exactly how we're gonna test the CMP sensor.

To do that, we'll tap into the tan with yellow stripe (TAN/YEL) wire on the sensor's 3-wire connector.

IMPORTANT: This test only works if the sensor stays plugged into its 3-wire engine wiring harness connector. You'll need to back probe the wire or use a wire-piercing probe to read the CMP signal inside the signal 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).

OK, let's get this pot of water boiling:

1. 1

   Connect the black lead from your multimeter to the battery's negative (-) post.

2. 2

   Disconnect the ignition coil from its connector. That way the engine doesn't start and you stay safe while testing the signal.
   
   NOTE: Don't remove the distributor cap —it needs to stay in place so the camshaft position sensor stays mounted tight.

3. 3

   Switch your multimeter to read DC voltage.

4. 4

   Use the red meter lead to probe the tan with yellow stripe (TAN/YEL) wire that comes out of the CMP sensor's connector.
   
   NOTE: The sensor needs to stay plugged into the harness for this to work. You'll have to back probe or pierce the wire to get a reading on the signal.

5. 5

   Have someone crank the engine for a few seconds while your leads stay in place.

6. 6

   Your multimeter should show the voltage flipping between 5 Volts and 0 Volts DC while the engine's cranking.

Here's how to read those results:

CASE 1: The CMP sensor is generating an ON/OFF voltage signal. That's a good sign. The camshaft position sensor is doing its job.

If your van still won't start, then the CMP sensor isn't the problem —something else is keeping the engine from firing up.

CASE 2: The CMP sensor IS NOT generating an ON/OFF signal. That almost always points to a bad sensor.

But before we call it bad for sure, we need to double-check that it's getting both power and Ground. Head over to the next step here: TEST 2: Making Sure The CMP Sensor Has 8 Volts.