Troubleshooting the camshaft position (CMP) sensor on your 1996–1997 3.9L V6 Dodge Ram van is easier than you think! You don't need an expensive scan tool —just a multimeter.
In this tutorial, you'll learn how to check the CMP sensor with three quick multimeter tests. Everything is explained step-by-step so you can figure out if the sensor is working or if it needs to be replaced.
Plus, I'm also gonna show you where to find a replacement camshaft position sensor that won't break the bank.
NOTE: The camshaft position sensor's also called the distributor pickup coil.
Contents of this tutorial:
- Symptoms Of A Bad Camshaft Position (CMP) Sensor.
- What the CMP Sensor Does.
- Circuit Descriptions Of The Camshaft Position Sensor.
- Where To Buy The Camshaft Position Sensor.
- TEST 1: Testing The Camshaft Position Signal.
- TEST 2: Making Sure The CMP Sensor Has 5 Volts.
- TEST 3: Making Sure The CMP Sensor Has Ground.
- More 3.9L V6 Dodge Ram Van Diagnostic Tutorials.
APPLIES TO: This tutorial applies to the following vehicles:
- 3.9L V6 Dodge Ram B1500 Van: 1995, 1996, 1997.
- 3.9L V6 Dodge Ram B2500 Van: 1995, 1996, 1997.
IGNITION SYSTEM WIRING DIAGRAMS:
- Ignition System Wiring Diagram (1996 3.9L V6 Dodge Ram Van).
- Ignition System Wiring Diagram (1997 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 (1992-1995 3.9L V6 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
As soon as you turn the key and the engine starts cranking, the fuel injection computer looks for a signal from the CMP sensor. If that signal's not there, it flags one of these diagnostic trouble codes (DTCs):
- P0340: No Camshaft Signal Detected By PCM.
- P1391: CMP Or CKP Signal Dropping In And Out.
When the CMP sensor (a.k.a. The distributor pickup coil) starts going bad, you'll usually see one or more of these engine performance problems:
- Cranks but won't fire up: The engine turns over, but it never actually starts.
- Random stalling: Everything runs fine... then boom, the engine just dies. Usually happens while idling or just as you're stepping on the gas pedal.
- Check Engine Light (CEL): A missing or inconsistent CMP signal usually lights up the CEL and of course, you'll see a P0340 or P1391 stored in the computer's memory.
- Rough idle or misfiring: When the CMP signal's weak, fuel and spark timing is affected. You'll feel the van's engine shake at idle, sputter during takeoff, or misfire when under load.
- Hard to start (cold or hot): Although the sensor still generates a signal, it's glitchy. So the engine starts, but only after long cranking.
- Sluggish throttle response: A glitchy CMP signal makes the engine feel slow or uneven when you hit the gas.
What the CMP Sensor Does
In a nutshell, the CMP sensor feeds the engine's computer the info it needs to time fuel injection and spark.
Here's what it does behind the scenes:
- Delivers the Fuel Sync Signal:
- As the engine spins, the CMP sensor generates a digital pulse called the fuel sync signal.
- This pulse tells the PCM exactly which cylinder is in the compression stroke —critical for fuel injector and spark timing.
- Works with the Crankshaft Sensor (CKP):
- The CKP sensor, down by the flywheel, tracks crankshaft speed and position.
- But it doesn't know which stroke each piston is in.
- That's where the CMP steps in, giving the PCM the missing piece to sync spark and fuel precisely.
- Tells the PCM when to fire each injector:
- With the CMP signal, the computer knows exactly when to pulse fuel into each cylinder.
- No signal? Then injector timing falls apart —or fuel delivery stops completely.
- Supports spark timing (indirectly):
- Spark timing mainly depends on the CKP sensor, but the CMP sensor adds cylinder position so everything stays in sync.
Circuit Descriptions Of The Camshaft Position Sensor
Here's a quick look at what each of those three wires is for:
| 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 |
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
When testing the CMP sensor, the thing is to remember is that it sends out a voltage signal that flips ON and OFF while the engine turns.
- ON means 5 Volts DC.
- OFF drops it down to 0 Volts.
The cool part? You can actually catch that voltage flipping —from 5 to 0 and back— using a regular multimeter. That's exactly how we're gonna test it.
If that signal isn't switching between 5 Volts and 0 Volts while cranking, then we'll move on to TEST 2 to check if the sensor's really getting power.
The wire you'll probe for the signal is the tan with yellow stripe (TAN/YEL).
IMPORTANT: Don't unplug the sensor. It's gotta stay connected for signal test to work. You'll need to back probe the wire or use a piercing probe to read the signal without disconnecting anything. You can see an example of a wire piercing probe (and where to buy it) here: Wire Piercing Probe.
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).
Here's how to do the test:
- 1
Unplug the ignition coil from its connector. This keeps the engine from starting while you test the signal output —super important, don't skip it!
NOTE: Leave the distributor cap in place. It holds the cam sensor steady, so don't mess with it. - 2
Connect your multimeter's black lead to the battery's negative (-) terminal.
- 3
Switch the multimeter to DC Volts mode.
- 4
Use the red lead to probe the TAN/YEL (tan with yellow stripe) wire coming out of the cam sensor's plug.
NOTE: Keep the sensor connected to the engine harness during the test. You'll have to back probe or pierce the wire to read the signal. - 5
Have a helper crank the engine once your probes are in place.
- 6
Watch the multimeter —you should see it flip between 5 Volts and 0 Volts DC as the engine turns over.
Alright, let's go over what your CMP signal test results actually tell you:
CASE 1: You saw the voltage flip between ON and OFF. That's exactly what you're looking for.
If you got that reading, the CMP sensor's working like it should. It's not the reason your engine isn't starting.
CASE 2: No ON/OFF voltage showing on the meter. That usually means the camshaft position sensor has failed.
But don't rush to replace it just yet —make sure it's actually getting power and Ground first. To check that, go to: TEST 2: Making Sure The CMP Sensor Has 5 Volts.