How To Test The MAP Sensor (1996-2000 3.8L V6 Chrysler, Dodge, Plymouth Mini-Van)

Testing the MAP sensor, on the 3.8L V6 Grand Caravan (Town & Country, Grand Voyager), is not difficult since it's very easy to access it.

In this tutorial I'll explain the 3 easy tests you need to perform to find out if it's bad or not.

Also, you don't need a scan tool to test the MAP sensor. I'll show you how to test it using a multimeter.

If your check engine light is illuminated by a P0108 or a P0109 diagnostic trouble code, this is the tutorial you need.

You can find this tutorial in Spanish here: Cómo Probar El Sensor MAP (1996-2000 3.8L V6 Chrysler, Dodge, Plymouth Mini-Van) (at: autotecnico-online.com).

APPLIES TO: This MAP sensor test tutorial applies to the following vehicles:

1. 3.8L V6 Chrysler Town & Country: 1996, 1997, 1998, 1999, 2000.
2. 3.8L V6 Dodge Grand Caravan: 1996, 1997, 1998, 1999, 2000.
3. 3.8L V6 Plymouth Grand Voyager: 1996, 1997, 1998, 1999, 2000.

NOTE: If you need the MAP sensor test for the 2001-2004 3.8L Chrysler and Dodge mini-vans, consult this tutorial: How To Test The MAP Sensor (2001-2004 3.8L V6 Chrysler, Dodge Mini-Van).

Symptoms Of A Bad MAP Sensor

The 3.8L V6 engine, covered by this tutorial, uses a 'speed density' fuel injection system.

What this means in plain English, is that the fuel injection computer needs to know 3 things to calculate the amount of air entering the engine and to calculate the amount of fuel to inject into the engine.

Those three things are: intake air temperature, engine RPM, and engine load.

The MAP sensor is the one tasked with informing the computer the engine load. It does this by measuring the amount of intake manifold pressure.

Since the MAP sensor is a critical component of the fuel injection system, when it fails the engine is going to suffer one or more of the following symptoms:

1. MAP sensor diagnostic trouble code (DTC) stored in the vehicle's computer's memory:
   1. P0107: MAP Sensor Voltage Too Low.
   2. P0108: MAP Sensor Voltage Too High.
2. Bad gas mileage.
3. Black smoke coming out of the tail pipe, especially when you accelerate the vehicle.
4. No power and/or hesitation as you accelerate the vehicle. It feels like all of a sudden someone cut the power out momentarily as you step on the gas to get the vehicle moving.

How The MAP Sensor Works

The manifold absolute pressure (MAP) sensor's job is to measure the amount of vacuum that is created by the downward stroke of the engine pistons and is one of the most important inputs the PCM needs to make you car or mini-van run optimally.

So here, in a nutshell, is how the MAP sensor works when you crank and start your 3.8L V6 Chrysler (Dodge, Plymouth) mini-van:

1. The fuel injection computer supplies 5 Volts and Ground to the MAP sensor.
2. At idle the MAP sends the PCM computer a DC voltage signal of about 1.1 to 1.8 Volts.
3. When you step on the accelerator pedal to accelerate the engine, vacuum immediately increases which causes the MAP signal voltage to the computer to decrease.
4. With this decreasing voltage signal, the computer knows it's time to inject more fuel, advance ignition timing, and a host of other things it has to do to keep your Chrysler (Dodge, Plymouth) mini-van running optimally.
5. As you let go off the accelerator pedal to slow down, the throttle plate closes and of course the MAP sensor sends the info to the computer as it returns to its idle voltage signal, till the whole cycle begins again.

Pretty easy stuff? The cool thing is that testing the MAP sensor's performance is as easy too.

Where To Buy The MAP Sensor And Save

The following links will help you to comparison shop for the MAP sensor and save a few bucks!:

If you're not sure if the above MAP sensor fit your particular 3.8L V6 Chrysler (Dodge, Plymouth) mini-van don't worry, once you get to the site, they'll make sure the sensor is the right one, if not, they'll find you the right one.

TEST 1: Checking The MAP Signal With A Multimeter

The very first thing that we're going to do is remove the MAP sensor from the intake manifold and then connect a multimeter to the MAP signal voltage wire.

Then we're going to manually apply vacuum to the sensor.

The purpose of this test, is to see if the MAP signal voltage reacts to the vacuum that we're going to apply and release to the MAP sensor.

Generally, when the MAP sensor fails, the MAP signal voltage will stay stuck in one value no matter how much vacuum is applied to the sensor.

The correct and expected test result is for the MAP signal voltage to decrease as vacuum is applied to it and for the voltage to increase (back to the original value) as vacuum is released.

This is a pretty easy test and on which should take you about 15 minutes or less to do. If you don't own a vacuum pump, don't worry. You can apply vacuum to the MAP sensor with your mouth or you can rent one from your local AutoZone (or O'Reilly Auto Parts).

NOTE: You'll need a multimeter to test your vehicle's MAP sensor. If you don't have one and need to buy one or upgrade yours, the following recommendation will help: Buying A Digital Multimeter For Automotive Diagnostic Testing.

IMPORTANT: The MAP sensor must remain connected to its electrical connector to read its voltage signal. You'll need to use a back-probe on the connector or a wire-piercing probe on the wire to access the MAP signal. You can see an example of this tool here: Wire Piercing Probe Review.

OK, let's start:

1. 1

   Remove the MAP sensor from the intake manifold. If you needed to disconnect the MAP sensor from it's electrical connector to remove it, reconnect it now (the MAP sensor must remain connected to its connector for this test).

2. 2

   Select Volts DC Mode on your multimeter.

3. 3

   Connect the red multimeter test lead to the dark green with red stripe (DK GRN/RED) wire of the MAP sensor's connector.
   
   NOTE: The MAP sensor must remain connected to its electrical connector to test the MAP signal voltage.

4. 4

   Ground the black multimeter test lead on the battery negative (-) terminal.

5. 5

   Have your helper turn the key On but don't start the engine.

6. 6

   You should see a voltage around 4.5 Volts DC registering on your multimeter. If it doesn't, don't worry about it just yet, continue with the other steps.

7. 7

   Connect your vacuum pump to the MAP sensor using a large diameter hose (I use a 3/8 fuel hose).
   
   Whatever hose you use, it's important that it makes a tight seal on both the MAP sensor's vacuum inlet nipple and the vacuum hose.

8. 8

   Apply vacuum to the MAP sensor till the gauge's needle reaches 5 in. Hg of vacuum. These are the readings you should have as you pump the vacuum pump to different vacuum levels:
   
   1.) 0 in. Hg ...... 4.7 Volts.
   
   2.) 5 in. Hg ...... 3.9 Volts.
   
   3.) 10 in. Hg .... 3.0 Volts.
   
   4.) 15 in. Hg .... 1.1 Volts.

9. 9

   Release the vacuum you've applied. The voltage reading should go back up to the value you registered in step 6.

Let's take a look at what your test results mean:

CASE 1: As you applied/released vacuum, the voltage decreased/increased. This is the correct test result.

You can conclude that the manifold absolute pressure (MAP) sensor is working fine and is not defective. No further MAP sensor tests are needed.

Now, if the MAP sensor trouble code won't go away, take a look at the info found at: MAP Code Will Not Go Away for a few more suggestions as to what could be causing the MAP sensor diagnostic trouble code (DTC).

CASE 2: As you applied/released vacuum, the voltage DID NOT decrease/increase. This test result usually confirms that the MAP sensor is fried and that it needs to be replaced. But before you replace it, make sure it's getting 5 Volts and Ground.

The next test is to make sure that the MAP sensor is getting 5 Volts. Go to: TEST 2: Making Sure The MAP Sensor Is Getting 5 Volts.

CASE 3: If the multimeter DID NOT register any voltage. This isn't good, but doesn't condemn the manifold absolute pressure (MAP) sensor as bad yet.

The next test is to make sure that the MAP sensor is getting 5 Volts. Go to: TEST 2: Making Sure The MAP Sensor Is Getting 5 Volts.