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

TEST 2: Making Sure The MAP Sensor Is Getting 5 Volts

The MAP sensor needs 5 Volts DC to create its vacuum voltage signal.

In this test section, we're going to make sure that the MAP sensor is getting them.

The wire that provides these 5 Volts DC, to the MAP sensor, is the violet with white stripe (VIO/WHT) wire of the sensor's 3-wire connector.

In the photo above, the female terminal labeled with the number 2 is the one that connects to the VIO/WHT wire.

We'll do a simple multimeter voltage test to find out if these 5 Volts are present in the violet with white stripe wire.

If 5 Volts are present in the wire, the next step is to make sure that the MAP sensor is getting Ground on the black with light blue stripe wire.

These are the test steps:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

   Disconnect the MAP sensor from its electrical connector.

3. 3

   Gently probe the terminal labeled number 2 in the photo above with the red multimeter test lead.
   
   NOTE: Be careful and don't damage the female terminal.

4. 4

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

5. 5

   Have a helper turn the key on but don't start the engine.

6. 6

   The multimeter should display 4.5 to 5 Volts on its screen.

Let's examine your test result:

CASE 1: The multimeter registered 4.5 to 5 Volts. This is the correct test result and confirms that the fuel injection computer and the circuit (wire) is supplying the MAP sensor with power.

The next step is to make sure that the manifold absolute pressure (MAP) sensor is getting Ground. For this test go to: TEST 3: Making Sure The MAP Sensor Is Getting Ground.

CASE 2: The multimeter DID NOT register 4.5 to 5 Volts. Without these 5 Volts the manifold absolute pressure sensor will not function.

The two most likely reasons for this are: 1) an open-circuit problem in the wire or 2) the fuel injection computer may be fried.

Altho' it's beyond the scope of this tutorial to test these two conditions, you have now eliminated the manifold absolute pressure (MAP) sensor on your 3.8L V6 Chrysler (Dodge, Plymouth) mini-van as being the cause of the problem and/or the MAP sensor diagnostic trouble code (DTC) lighting up the check engine light (CEL).

TEST 3: Making Sure The MAP Sensor Is Getting Ground

If you've reached this point, you have confirmed that:

• The MAP signal voltage does not decrease/increase as you apply/release vacuum to the sensor.
• The MAP sensor is getting 5 Volts from the VIO/WHT wire.

In this last test section, we're going to make sure that the MAP sensor is getting Ground.

The wire that provides Ground to the MAP sensor, is the the black with light blue stripe (BLK/LT BLU) wire of the sensor's 3-wire connector

In the photo above, the black with light blue stripe wire connects to the female terminal labeled with the number 1.

IMPORTANT: If you probe the front of the female terminal, probe it very gently with your multimeter test leads. Or you run the risk of damaging the terminal.

CAUTION: The fuel injection computer provides Ground for the MAP sensor. Be careful and don't short the wire to battery 12 Volts or you'll fry the computer. The multimeter voltage test I'm suggesting is a safe way to test for Ground in this wire.

Let's get testing:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

   Disconnect the MAP sensor from its electrical connector.

3. 3

   Gently probe the terminal labeled number 1 in the photo above with the black multimeter test lead.
   
   NOTE: Be careful and don't damage the female terminal.

4. 4

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

5. 5

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

6. 6

   Your multimeter should display 10 to 12 Volts if Ground is present.

Let's examine your test result:

CASE 1: The multimeter showed 10 to 12 Volts. This is the correct test result and tells you that the fuel injection computer and the wire/circuit (that supply this Ground) are OK.

This multimeter test result also confirms that the MAP sensor is bad and needs to be replaced if you have confirmed:

• That the MAP voltage signal does not decrease when you apply vacuum to the MAP sensor (TEST 1).
• That the VIO/WHT wire is supplying 5 Volts DC (TEST 2).
• That the BLK/LT BLU wire is supplying Ground.

Check out my MAP sensor recommendations: Where To Buy The MAP Sensor And Save.

CASE 2: The multimeter DID NOT show 10 to 12 Volts. This test result indicates a problem with either the PCM (internal fault/problem) or an open in the wire between the MAP sensor and the PCM itself.

Altho' testing these two conditions are beyond the scope of this tutorial, you have now eliminated the MAP sensor on your 3.8L V6 Chrysler (Dodge Plymouth) mini-van as being the cause of the problem and/or the MAP sensor diagnostic trouble code (DTC) lighting up the check engine light (CEL).

MAP Sensor Code Won't Go Away

Nothing is more frustrating than replacing the MAP sensor (and erasing the trouble code) and then having the MAP sensor code come back during your road test.

Why does it happen? Usually because the MAP sensor is just reporting the effect that a problematic mechanical condition is having on the engine's ability to create vacuum inside the intake manifold.

Here are a few suggestions on what to check (if this is what's happening in your specific situation):

• Check the MAP sensor's O-ring. There's a good chance that the o-ring on the MAP sensor's vacuum inlet nipple (the part that goes into the intake manifold to sense the vacuum) is torn, missing or distorted. When this happens, ambient air will leak into the intake manifold and skew the MAP sensor's readings.
• Check engine compression. Worn or damaged cylinder head valves or piston rings will cause the engine to produce erratic and low vacuum readings that can fool the fuel injection computer into thinking the MAP sensor is bad.
• The MAP sensor is failing intermittently. Which means that it works fine most of the time, but every now and then it doesn't:
  • I have found that the best way to test these intermittent failures is to slightly tap the MAP sensor with the handle of a screw-driver and see if this tapping screws up the voltage readings as I apply vacuum.
• Check the MAP sensor's connector. See if the MAP sensor connector is broken (this could be causing an intermittent open-circuit or short-circuit problem in the MAP signal wire). This usually happens when the MAP sensor's electrical connector's locking tab has broken.
• Check the fuel pump's pressure with a fuel pressure test gauge. The second most common cause of a MAP sensor code is a lean air/fuel mixture caused by a failing fuel pump. Most of the time a fuel pump will fail completely and the engine won't start, but not always. The fuel pump can slowly fail and not send enough fuel to keep the engine humming along nicely. To check for this, I recommend a fuel pressure test.