How To Test The MAP Sensor (2002-2003 4.7L V8 Dodge Ram Pickup)

  • By: Abraham Torres-Arredondo
  • Created: 03 July 2025
  • Updated: 03 July 2025
  • Articl Id: 851
How To Test The MAP Sensor (2002, 2003 4.7L V8 Dodge Ram Pickup)

If your 2002–2003 4.7L V8 Dodge Ram pickup is lighting up the check engine light with a P0107 or P0108 trouble code, there's a good chance the MAP (Manifold Absolute Pressure) sensor is toast.

These two codes mean the PCM (Powertrain Control Module) is seeing MAP sensor readings that don't make sense —either too low (P0107) or too high (P0108) for current engine conditions.

This tutorial will help you figure out what's really going on. You'll learn how the MAP sensor works, what can cause it to fail, and how to test it accurately using nothing more than a basic multimeter and vacuum pump —no expensive diagnostic tools needed.

Whether you're a DIYer or a seasoned tech, you'll find practical tips, step-by-step test instructions, and real-world advice to help you fix the problem without wasting time or money on parts you might not need.

Contents of this tutorial:

APPLIES TO: This tutorial applies to the following Dodge Ram pickups:

  • 4.7 V8 Dodge Ram 1500 Pickup: 2002, 2003.

SENSOR POWER/GROUND CIRCUIT WIRING DIAGRAMS:

2004-2009 MAP SENSOR TESTS:

MAP CODE WON'T GO AWAY:

Symptoms Of A Bad MAP Sensor

When the MAP (Manifold Absolute Pressure) sensor starts to fail on your 2002–2003 4.7L V8 Dodge Ram pickup, you'll usually notice a change in the way your truck drives.

This engine uses a speed density fuel injection system, which means it depends heavily on accurate readings from the MAP sensor to calculate how much fuel to inject. When that signal goes bad, it throws off the whole air/fuel strategy —and that can lead to all kinds of driveability problems.

The most common trouble codes related to a faulty MAP sensor are:

  • P0107 – MAP Sensor Circuit Low Voltage.
  • P0108 – MAP Sensor Circuit High Voltage.

If you're seeing either of these codes and want a deeper breakdown of what they mean and what causes them, check out these guides:

Here are the symptoms you might experience when the MAP sensor signal is off:

  • Engine hesitation or stumbling during acceleration.
  • Rough or unstable idle.
  • Poor fuel economy.
  • Check engine light (CEL) on with code P0107 or P0108.
  • Black smoke from the tailpipe in some cases.
  • Hard starting or extended crank time.
  • Engine may feel sluggish or low on power.

Keep in mind, these symptoms can be caused by other issues too, like vacuum leaks or wiring problems. That's why it's important to test the MAP sensor before replacing it.

In the next section, we'll talk about whether it's smarter to replace the sensor outright or take a few minutes to test it first.

Should I Just Replace The MAP Sensor?

I'll be very frank —most folks (even some shops) go straight to replacing the MAP sensor when they see a P0107 or P0108 code. And truthfully, in many cases, that solves the issue right away.

There's nothing wrong with that approach. The MAP sensor on the 2002–2003 4.7L V8 Dodge Ram is easy to get to, simple to swap out, and not that expensive. If you just want to fix the problem and move on, I totally get it.

If you're heading that route, here are a couple of MAP sensors I recommend. These are quality parts that fit your truck and come from brands I trust:

Buying through one of these links helps support the site —at no extra cost to you— and keeps these tutorials coming. Thank you!

That said, if you're the type who wants to be 100% sure before buying anything, I recommend testing the MAP sensor first. It's not difficult, doesn't require any expensive tools, and it can save you money and guesswork —especially if the real issue is wiring or a power/Ground problem.

In this section, I'll walk you through the first test: TEST 1: Checking The MAP Sensor Signal.

Where To Buy The MAP Sensor And Save

You can find the MAP sensor just about in anywhere. The best place to buy it and save a few bucks is is online.

The following links will help you comparison shop for the MAP sensor:

Standard Motor Products AS158 MAP Sensor
Standard Motor Products AS158 MAP Sensor
Walker Products 225-1040 Manifold Absolute Pressure Sensor
Walker Products 225-1040 Manifold Absolute Pressure Sensor

Disclosure: As an Amazon Associate, I earn from qualifying purchases. Buying through these links helps support this site at no extra cost to you. I truly appreciate it!

Not sure if the MAP sensor fits your particular vehicle? Don't worry, once you get to the site they'll make sure it fits by asking you the specifics of your particular GM vehicle. If it doesn't fit, they'll find you the right MAP sensor.

TEST 1: Checking The MAP Sensor Signal

Checking The MAP Sensor Signal. How To Test The MAP Sensor (2002, 2003 4.7L V8 Dodge Ram Pickup)

To find out if the MAP sensor is really behind the codes P0107 or P0108, we're gonna check the signal it's creating and sending to the PCM on the green with red stripe (DK GRN/RED) wire.

This quick test will show you if the sensor is responding correctly to changes in vacuum —or if it's feeding the PCM bad info that's triggering those codes.

All you need is a basic multimeter and a handheld vacuum pump to get the job done. In this section, I'll walk you through exactly how to do it, step by step.

If you don't have those tools, here are a couple I recommend and personally use:

They're reliable and affordable, and when you buy through these links, it helps support this site at no extra cost to you —thanks!

NOTE: The vacuum inlet port on the MAP sensor is larger than the hose that typically comes with a handheld vacuum pump. To connect them, you'll need some kind of adapter. I use an old spark plug boot from a discarded plug wire —it fits snugly and does the job perfectly. You can use anything similar to step up or step down the hose size as needed.

OK, these are the test steps:

  1. 1

    Remove the MAP sensor from the intake manifold so you can access its vacuum port.

  2. 2

    Connect a handheld vacuum pump to the MAP sensor's vacuum port using a short length of hose.

    Make sure the MAP sensor stays connected to its electrical connector.

  3. 3

    Set your multimeter to DC Volts mode (20V range works well).

  4. 4

    Ground the black multimeter lead by connecting it directly to the battery's negative (-) terminal.

  5. 5

    Gently back-probe the DK GRN/RED wire at the MAP sensor connector using the red multimeter lead.

  6. 6

    Turn the ignition key to the ON position —but don't start the engine.

  7. 7

    Your multimeter should now read about 3.8 to 4.0 Volts DC with no vacuum applied.

  8. 8

    Begin applying vacuum using the hand pump.

  9. 9

    As vacuum increases, the voltage should drop —down to around 1.1 Volts at maximum vacuum.

  10. 10

    Release the vacuum completely.

  11. 11

    The voltage should rise again, returning to the original 3.8–4.0 Volt range.

  12. 12

    Repeat the vacuum apply/release process several times. Each time, you should see the voltage drop and rise smoothly.

Here's what your test result means:

CASE 1: The voltage dropped as you applied vacuum, and rose again when you released it. This tells you the MAP sensor is working like it should since it's correctly responding to changes in vacuum —just like the PCM expects.

So, if you're still seeing a MAP sensor code (like P0107 or P0108), check out this guide —there's probably something else going on:

CASE 2: Voltage stayed stuck —didn't change as you applied or released vacuum. This usually means that your MAP sensor is bad and confirms that codes P0108 or P0107 are telling the truth.

To be absolutely sure the MAP sensor is toast, we need to make sure it's getting power. Go to: TEST 2: Verifying The MAP Sensor Is Getting Power.

CASE 3: Multimeter read 0 Volts from the signal wire. This usually means one of two things: either the sensor is completely dead or it's not getting power or Ground.

To confirm, you'll want to check the 5 Volt supply and the Ground circuit next. Start with: TEST 2: Making Sure The MAP Sensor Is Getting Power.

TEST 2: Verifying The MAP Sensor Is Getting Power

Verifying The MAP Sensor Is Getting Power. How To Test The MAP Sensor (2002, 2003 4.7L V8 Dodge Ram Pickup)

So, in TEST one, the MAP sensor's voltage signal did not change as expected, and this could be due to it being toast, or it might not be getting power or Ground.

To be sure, before we spend any money on a new sensor, we need to make sure it's actually getting the power it needs to work properly. Without this 5 Volt supply, the sensor can't send any meaningful signal to the PCM.

On your 2002–2003 4.7L V8 Dodge Ram pickup, the MAP sensor receives its 5 Volt reference from the PCM through the orange (ORG) wire of it's 3-wire connector.

Here's how to check for that voltage with a multimeter:

  1. 1

    Disconnect the MAP sensor from its electrical connector.

  2. 2

    Set your multimeter to Volts DC mode.

  3. 3

    Turn the key ON but don't start the engine.

  4. 4

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

    You can also connect it to a clean, rust-free, and paint-free metal surface on the engine block.

  5. 5

    Carefully probe the front of the terminal that connects to the ORG wire with the red multimeter lead.

  6. 6

    Your multimeter should read between 4.5 and 5.0 Volts DC.

Now, let's make sense of what you just measured:

CASE 1: You have 5 Volts at the ORG wire. This confirms the PCM is sending power to the MAP sensor.

Now, for your next step, we need to make sure the MAP sensor is getting Ground from the black with light blue (BLK/LT BLU) wire of its connector. Go to: TEST 3: Making Sure The MAP Sensor Is Getting Ground.

CASE 2: You don't have 5 Volts at the ORG wire. Recheck your connections and try again.

If you still don't see the 5 Volts on your multimeter, you've likely got an open or short in the 5 Volt supply circuit between the PCM and sensor —or a rare PCM issue.

In this case, the MAP sensor isn't the problem, and replacing it won't solve the issue. Your next step is to check the continuity of the ORG wire between the PCM connector and the MAP sensor connector.

To help you do that, here are two detailed wiring diagrams that show the sensor power and Ground circuits for each model year:

TEST 3: Making Sure The MAP Sensor Is Getting Ground

Making Sure The MAP Sensor Is Getting Ground. How To Test The MAP Sensor (2002, 2003 4.7L V8 Dodge Ram Pickup)

Now that you've confirmed the MAP sensor is getting its 5 Volt supply, the next step is to make sure it also has a reliable Ground. Without Ground, the sensor can't complete the circuit or send a signal back to the PCM.

On your 2002–2003 4.7L V8 Dodge Ram pickup, the sensor gets its Ground through the black with light blue stripe (BLK/LT BLU) wire —and it's also shared with other sensors on the engine.

CAUTION: The MAP sensor gets its Ground from the PCM, so never connect the BLK/LT BLU wire directly to battery power —doing so will damage the PCM. The multimeter voltage test below is a safe and reliable way to check for Ground on this circuit.

Here's how to test for Ground using your multimeter:

  1. 1

    Leave the MAP sensor disconnected from its harness connector.

  2. 2

    Set your multimeter to Volts DC mode.

  3. 3

    Turn the key ON but don't start the engine.

  4. 4

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

  5. 5

    Use the black multimeter lead to gently probe the front of the terminal that connects to the BLK/LT BLU wire at the MAP sensor connector.

  6. 6

    Your multimeter should read between 10 to 12 Volts DC.

Let's find out what it all means:

CASE 1: You have 10 to 12 Volts on your meter when testing the BLK/LT BLU wire. This means the MAP sensor has a solid Ground path.

And with this, you've confirmed all three key things:

  • In TEST 1, the MAP sensor signal didn't respond to vacuum changes.
  • In TEST 2, the sensor was getting a steady 5 Volts DC.
  • And now in TEST 3, we've verified that it's getting a good Ground.

That means the MAP sensor is bad —it's not doing its job and needs to be replaced.

If you're ready to replace it, here are a couple of MAP sensors I recommend. Buying through these Amazon affiliate links helps support the site at no extra cost to you —and I truly appreciate it:

CASE 2: You don't get a 10 to 12 Volt reading. That means Ground isn't reaching the MAP sensor.

Recheck your connections and test again. If you still get no reading, the issue isn't the sensor. You'll need to trace the wire back to the PCM to check for damage or corrosion.

To help you do that, here are two detailed wiring diagrams that show the sensor power and Ground circuits for each model year:

More 4.7L V8 Dodge Ram Pickup Diagnostic Tutorials

If you're tackling a check engine light or just want to learn more about how your 4.7L Dodge Ram works, this index can really help. It's packed with practical tutorials written for DIYers and Pros alike.

Below are just a few of the tutorials you'll find in the index:

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