How To Test The Camshaft Position Sensor (1998-2003 5.2L, 5.9L V8 Dodge Ram Pickup)

Testing the camshaft position (CMP) sensor to see if it's good or bad on the 1998-2003 5.2L/5.9L V8 Dodge Ram pickup is a pretty simple process.

In this guide, I'm gonna walk you through three easy tests you can do with just a multimeter (no scan tool required). With your test results, you'll quickly find out if the CMP sensor is working or not.

I'll also point you to where you can pick up a replacement sensor without spending too much.

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

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

• Dodge Ram 1500 Pickup 5.2L V8: 1998, 1999, 2000, 2001.
• Dodge Ram 2500 Pickup 5.2L V8: 1998.
• Dodge Ram 1500 Pickup 5.9L V8: 1998, 1999, 2000, 2001, 2002, 2003.
• Dodge Ram 2500 Pickup 5.9L V8: 1998, 1999, 2000, 2001, 2002.
• Dodge Ram 3500 Pickup 5.9L V8: 1998, 1999, 2000, 2001, 2002, 2003.

OTHER CMP SENSOR TESTS:

• How To Test The Distributor Pickup Coil (1989-1991 5.2L, 5.9L V8 Dodge Ram Pickup).
• How To Test The Camshaft Position Sensor (1992-1995 5.2L, 5.9L V8 Dodge Ram Pickup).
• How To Test The Camshaft Position Sensor (1996-1997 5.2L, 5.9L V8 Dodge Ram Pickup).

Symptoms Of A Bad CMP Sensor

The Camshaft Position (CMP) sensor on your 1998-2003 V8 Dodge Ram pickup is located inside the distributor and plays a critical role in synchronizing fuel injection with the engine's mechanical rotation.

It works together with the crankshaft position (CKP) sensor to ensure fuel is injected into the correct cylinder at the right time.

Usually, but not always, when the CMP sensor fails, you'll see the following trouble code stored in the computer's memory:

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

Here are a few other common symptoms you'll see:

• Engine cranks but won't start: The engine turns over, but that's all —it doesn't start because the fuel injectors aren't firing properly. The PCM can't figure out the right cylinder timing. You might still see spark at the spark plug wires, but fuel delivery is out of sync.
• Intermittent stalling: Engine may run fine, then suddenly stall, especially at idle or low RPMs. The PCM may lose track of the fuel sync signal, causing injectors to misfire or shut down temporarily.
• Check Engine Light (CEL): If the PCM sets a trouble codes like P0340 (CMP Sensor Circuit) or P1391 (Intermittent Loss of CMP or CKP Signal), it'll illuminate the check engine light.
• Rough Idle or misfiring: If the sensor is providing a weak or erratic signal, fuel delivery can become inconsistent, leading to rough idle, hesitation, or misfires.
• Bad gas mileage: With incorrect fuel injector timing, the engine may waste fuel or run rich, leading to poor MPG and black smoke from the tailpipe.
• Hard starts (cold or hot): If the CMP sensor signal is weak but not completely dead, the engine may eventually start, but only after several cranks.
• Poor acceleration or hesitation: Since fuel injection is off-sync, you may notice flat spots in throttle response or sluggish acceleration.

What The CMP Sensor Does

The camshaft position (CMP) sensor on your 1998-2003 V8 Dodge Ram pickup is mounted inside the distributor (it used to be called the distributor pickup coil) and it plays a critical role in fuel injection timing.

Here's what it does:

• Sends a Fuel Sync Signal:
  • As the engine cranks or runs, the CMP sensor generates a signal called the fuel sync signal.
  • This signal tells the engine computer (PCM) which cylinder is on its compression stroke.
  • Without this signal, the PCM doesn't know when to fire each fuel injector.
• Works together with the CKP sensor:
  • Your engine also has a crankshaft position (CKP) sensor mounted near the flywheel.
  • The CKP sensor tells the PCM engine speed and crankshaft position.
  • But the CKP signal alone doesn't tell which cylinder is which.
  • That's where the CMP comes in —it gives the PCM the "reference point" it needs to match each crank rotation to the correct cylinder.
• Synchronizes fuel injection:
  • The CMP sensor helps the PCM sync fuel injection so each injector fires at the right time for its cylinder.
  • Without it, the engine may run poorly, or not run at all.
• Supports spark timing (indirectly)
  • While the crankshaft sensor handles most of the spark timing, the CMP sensor still plays a role by confirming cylinder position.

Circuit Descriptions Of The Camshaft Position Sensor

The camshaft position sensor needs power and Ground to activate and produce its signal. As such, it has 3 wires coming out of its electrical connector.

In the table below, you'll find a short description of each of the 3 wires:

Pin	Wire Color	Description
1	Tan with yellow stripe (TAN/YEL)	CMP Signal
2	Black with light blue stripe (BLK/LT BLU)	Sensor Ground
3	Violet with white stripe (VIO/WHT)	5 Volts DC

Where To Buy The Camshaft Position Sensor

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

TEST 1: Testing The Camshaft Position Signal

The CMP sensor sends out an ON/OFF voltage signal while the engine is cranking or running. When the signal's ON, it reads 5 Volts DC. When it's OFF, it drops to 0 Volts.

The good part? We can catch that ON/OFF voltage flip between 5 and 0 Volts using a multimeter —and that's exactly how we're gonna test it.

When the camshaft position sensor goes bad, it usually gets stuck showing just one voltage reading while the engine spins.

So for the first test, we'll hook up a multimeter to the CMP sensor's signal wire and watch if the voltage keeps switching between 5 and 0 Volts.

The wire you need to probe for the CMP sensor's ON/OFF signal is the tan with yellow stripe (TAN/YEL) wire.

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.

NOTE: Don't have a multimeter or need to upgrade yours? This is the one I use: Tekpower TP8268 AC/DC Auto/Manual Range Digital Multimeter with NCV Feature, Mastech MS8268 Upgraded, MS88 (at: amazon.com).

Here's how to run the test:

1. 1

   Attach the black lead of your multimeter directly on the battery's negative (-) terminal.

2. 2

   Unplug the ignition coil's electrical connector. This is an important safety precaution, so don't skip this step.
   
   NOTE: Don't take the distributor cap off. It needs to stay in place to hold the camshaft position sensor where it belongs.

3. 3

   Set your multimeter to DC Volts.

4. 4

   Connect the red multimeter lead to the tan with yellow stripe (TAN/YEL) wire coming from the CMP sensor's connector.
   
   NOTE: The cam sensor must stay plugged into its engine wiring harness connector so the signal can be measured.

5. 5

   Once the leads are connected, have your helper crank the engine for a few seconds.

6. 6

   If the sensor is working, the voltage should flip back and forth between 5 Volts and 0 Volts DC while the engine turns over.

Now let's look at what your test result means:

CASE 1: You see the voltage switching between 5 and 0 Volts. That's the result you want to see.

This confirms that the CMP sensor's working like it should. It's not the reason your pickup's engine isn't starting.

CASE 2: The voltage didn't switch between 5 and 0 Volts DC. That usually means the camshaft position sensor has failed.

Before swapping it out, make sure it's getting both power and Ground. To do that, move on to: TEST 2: Making Sure The CMP Sensor Has 5 Volts.