How To Test The MAP Sensor (1998-2003 5.2L, 5.9L V8 Dodge Ram Van)

Check engine light on and a MAP sensor trouble code (DTC) showing up? Engine running bad in your Dodge Ram van? Sounds like the MAP sensor has failed.

But heads up —that MAP trouble code might also come from another issue under the hood that's got nothing to do with the sensor itself.

The upside? Testing the MAP sensor on your van's engine is actually pretty easy. No scan tool needed —just a regular multimeter and a basic hand-held vacuum pump. In this guide, I'm gonna show you exactly how to test it, one step at a time.

APPLIES TO: This tutorial applies to the following vehicles:

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

OTHER MAP SENSOR TESTS:

• How To Test The MAP Sensor (1989-1990 5.2L, 5.9L V Dodge Ram Van).
• How To Test The MAP Sensor (1991 5.2L, 5.9L V8 Dodge Ram Van).
• How To Test The MAP Sensor (1992-1997 5.2L, 5.9L V8 Dodge Ram Van).

Symptoms Of A Bad MAP Sensor

When the MAP sensor fails, your van's computer will illuminate the check engine light (CEL) and stores one of these two diagnostic trouble codes (DTCs):

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

Along with throwing a MAP-specific code, a bad sensor can also cause any of the following issues:

• Rough idle: The engine might idle unevenly while you're sitting in Drive —like when you're waiting at a red light.
• Black smoke: You might see black smoke coming out of the exhaust, especially when hitting the gas and revving up the engine.
• Random stalling: The engine could cut out unexpectedly —whether you're cruising along or just starting to speed up.
• Stalls right after starting: It might crank and start fine, but then shut off.
• No power: The van can feels like it's got no power when accelerating —struggling to build up speed.
• Limp-In Mode: To protect the engine, the computer might activate limp mode —reducing performance and crushing your MPG.

NOTE: Don't forget —other engine issues (not tied to the MAP sensor at all) can still make the computer set a MAP trouble code. So before swapping it out with a new one, it's smart to test the sensor first.

In the next steps, I'll walk you through a quick and easy bench test so you can figure out if the MAP sensor's really the problem. If it passes, you'll know it's time to keep digging elsewhere.

• MAP Sensor Code Won't Go Away.

How The MAP Sensor Works

Your Dodge Ram van doesn't use a mass airflow (MAF) sensor to track how much air's coming into the engine. Instead, it runs on a Speed Density system.

With this setup, the fuel injection computer doesn't measure airflow directly. It estimates it by constantly checking three key inputs from these sensors:

• The manifold absolute pressure (MAP) sensor.
• The intake air temperature (IAT) sensor.
• The crankshaft position (CKP) sensor (for engine RPM input).

Using those signals, the computer figures out how much air the engine's pulling in, then calculates the right amount of fuel to inject.

Here's a quick look at what happens when you fire up the engine:

• MAP sensor gets powered: The computer sends both voltage and Ground to the MAP sensor to get it working:
  • 1997 vans: The violet wire with a white stripe (VIO/WHT) delivers 5 Volts DC to terminal 3 (see the wiring diagram above).
  • 1998 and newer vans: The orange (ORG) wire sends 5 Volts DC to terminal 3.
  • The black with light blue stripe (BLK/LT BLU) wire gives it a Ground and connects to terminal 1.
• Measuring vacuum: The MAP sensor starts checking the vacuum inside the intake manifold.
  • Idle RPM: At idle, the throttle is mostly closed, causing a strong vacuum to form in the intake manifold. This leads to reduced air pressure, prompting the MAP sensor to produce a low-voltage reading.
  • Acceleration: When the engine accelerates and the throttle opens, the vacuum level drops and manifold pressure rises. The MAP sensor reacts by increasing its voltage output to reflect the higher pressure conditions.
• Fuel control kicks in: The computer uses data from the MAP, IAT, and CKP sensors to calculate fuel delivery. It:
  • Adjusts the injector pulse width — that's how long the injectors stay open.
  • Tweaks ignition timing to smooth things out and boost fuel economy.

Now that you know how the system works behind the scenes, let's jump into the test steps!

Where To Buy The MAP Sensor And Save

Here are a few known automotive brand MAP sensors I suggest checking out:

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

TEST 1: Verifying The MAP Signal

First thing you're gonna do is check if your MAP sensor sends out a changing voltage signal when you apply vacuum by hand.

To run this test, you'll connect your multimeter up to the sensor's signal wire. Then, apply vacuum using a hand-held pump —or if you don't have one, you can pull vacuum by mouth.

Depending on whether the sensor's working or not, you'll get one of two results:

• Good Sensor: The voltage on your multimeter will drop when you apply vacuum and rise when you release it.
• Bad Sensor: If the sensor's toast, the voltage will stay stuck —it won't change no matter how much vacuum you apply.

NOTE: Need a multimeter or a vacuum pump (or thinking about upgrading)? These are the exact ones I personally use and recommend:

• Multimeter: Tekpower TP8268 AC/DC Auto/Manual Range Digital Multimeter (at: amazon.com).
• Vacuum pump: HTOMT 2 In 1 Vacuum Pump Test Set (at: amazon.com).

Here's how to test it step-by-step:

1. 1

   Remove the MAP sensor from the throttle body.

2. 2

   Connect your vacuum pump to the MAP sensor's vacuum port.
   
   IMPORTANT: Make sure the sensor stays plugged into its 3-wire connector the whole time.

3. 3

   Clip the black lead of your multimeter to the battery's negative (-) post.

4. 4

   Set your multimeter to DC voltage mode.

5. 5

   Connect the red multimeter lead to the center wire of the MAP sensor's connector.
   
   That center wire should be dark green with a red stripe (DK GRN/RED).
   
   NOTE: Use a back probe on the connector or a wire-piercing tool on the wire to make this connection. You can learn more about this tool here: Wire Piercing Probe.

6. 6

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

7. 7

   With the key ON and no vacuum applied, your multimeter should show around 4.5 to 4.7 Volts DC.

8. 8

   Now apply vacuum to the MAP sensor using the pump or your mouth. Watch the voltage drop with each level:
   
   1.) 0 in. Hg ...... 4.7 Volts
   2.) 5 in. Hg ...... 3.9 Volts
   3.) 10 in. Hg .... 3.0 Volts
   4.) 20 in. Hg .... 1.1 Volts
   
   NOTE: The voltage should smoothly drop as you add vacuum and rise again when you release it.

Now let's break down what your results mean:

CASE 1: Voltage changed as vacuum was applied and released. That's a solid sign your MAP sensor's doing its job!

If the MAP code's still showing and the check engine light's hanging around, head over here for the next step: MAP Sensor Code Won't Go Away.

CASE 2: Voltage didn't move at all. That usually means the MAP sensor's faulty.

To confirm, you'll want to check if the sensor's actually getting power and Ground. Start with: TEST 2: Making Sure the MAP Sensor is Getting Power.

CASE 3: You saw 0 Volts DC. That could mean the sensor's dead —or that it's not getting the voltage or Ground it needs.

Next move: test the power and Ground going to the MAP sensor. Go to: TEST 2: Making Sure That The MAP Sensor Is Getting Power.

TEST 2: Making Sure That The MAP Sensor Is Getting Power

At this point, you've confirmed that your MAP sensor isn't putting out a changing voltage —the reading stays the same no matter how much vacuum you apply.

Next up: check if the sensor's even getting power. Without voltage, it's not gonna do a thing.

The MAP sensor gets its power straight from the fuel injection computer. The FI computer sends a steady 5 Volts DC through one of these wires:

• 1997 Van: violet with white stripe (VIO/WHT).
• 1998 and newer: orange (ORG).

This 5 Volt feed is delivered by terminal 1 of the MAP sensor's 3-wire connector (see the illustration of the connector above).

Here's what we need to do:

1. 1

   Unplug the MAP sensor from its 3-wire connector.

2. 2

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

3. 3

   Switch your multimeter over to DC voltage mode.

4. 4

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

5. 5

   Use the red lead to probe terminal 1 on the MAP connector.
   
   NOTE: Double-check that the wire connecting to terminal 1 is either ORG or VIO/WHT, depending on the model year.

6. 6

   Your multimeter should read: 4.5 to 5 Volts DC.

Let's interpret your test results:

CASE 1: You got a solid 4.5 to 5 Volt reading. That means the FI computer is sending power to the MAP sensor.

Your next move is to make sure the sensor's getting a proper Ground signal too. Go to: TEST 3: Verifying The MAP Sensor Ground Circuit.

CASE 2: No voltage —nothing close to 5 Volts showed up. First, double-check your test setup and multimeter connections.

If you still see 0 Volts after checking everything, that's why your MAP sensor isn't producing it's variable voltage signal in TEST 1. No power = no signal.

That means the sensor itself isn't the issue. What you're really dealing with is a missing power supply. Here's what might be causing that:

• The 5 Volt wire is broken, shorted, or open somewhere between the MAP sensor and the computer.
• Less common, but possible —the fuel injection computer has an internal problem.