How To Test The MAP Sensor (1992-1996 3.9L Dodge Dakota)

TEST 2: Making Sure The MAP Sensor Has 5 Volts

If the MAP sensor did not produce a decreasing voltage signal as you applied vacuum to it, then there's a good chance that it might not be getting 5 Volts DC.

The wire that supplies voltage to the MAP sensor is the violet with white stripe (VIO/WHT) wire labeled with the number 1 in the photo above.

We're going to do a simple multimeter voltage test on this wire to check for the presence of 5 Volts.

If 5 Volts are present then our next step is to make sure that the MAP sensor is getting Ground (in TEST 3).

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

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

4. 4

   Connect the red multimeter test lead (using the appropriate tool) to the VIO/WHT wire.

5. 5

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

6. 6

   Your multimeter should read 4.5 to 5 Volts DC.

Let's analyze your test results:

CASE 1: 5 Volts are present. This is the correct test result.

Now that you have confirmed that your Dodge Dakota's MAP sensor is getting 5 Volts, the next step is to make sure it's getting Ground. Go to: TEST 3: Making Sure The MAP Sensor Has Ground.

CASE 2: 5 Volts are not present. Without these 5 Volts the MAP sensor will not function.

Although it's beyond the scope of this tutorial to troubleshoot these missing 5 Volts, the most likely cause is an open-circuit problem in the violet with white stripe (VIO/WHT) wire between the MAP sensor's connector and the fuel injection computer's connector.

TEST 3: Making Sure The MAP Sensor Has Ground

So far your tests have confirmed that:

• The MAP sensor is not creating a decreasing voltage signal as vacuum is applied to it.
• The MAP sensor is getting 5 Volts on the violet with white stripe (VIO/WHT) wire.

Our next and last step is to make sure that the MAP sensor is getting Ground.

The wire that supplies Ground to the MAP sensor is the black with light blue stripe (BLK/LT BLU) wire labeled with number 3 in the photo above.

NOTE: Ground is provided by your 3.9L Dodge Dakota's fuel injection computer. So be careful and do not apply battery power (12 Volts DC) to the Ground wire or you'll fry the computer. The voltage test I'm describing below (to test for Ground) is a safe way of verifying the presence of this Ground.

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

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

4. 4

   Connect the black multimeter test lead (using the appropriate tool) to the BLK/LT BLU wire.

5. 5

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

6. 6

   Your multimeter should read 10 to 12 Volts DC.

Let's analyze your test results:

CASE 1: Ground is present in the BLK/LT BLU wire. This is the correct test result.

You can correctly conclude that the MAP sensor is defective if you have:

• Confirmed that its MAP voltage signal does not decrease/increase as you apply/release vacuum to the MAP sensor (TEST 1).
• Confirmed that it's getting 5 Volts on the VIO/WHT wire (TEST 2).
• Confirmed that it's getting Ground on the BLK/LT BLU wire (this test).

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

CASE 2: Ground IS NOT present. Without Ground the MAP sensor will not function.

Although it's beyond the scope of this tutorial to troubleshoot this missing Ground, the most likely cause is an open-circuit problem in the BLK/LT BLU wire between the MAP sensor's connector and the fuel injection computer's connector.

More 3.9L Dodge Dakota Tutorials

You can find a complete list of 3.9L Dodge Dakota tutorials in this index:

• Chrysler 3.9L Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

• How To Test The Starter Motor (1991-1995 3.9L Dodge Dakota).
• How To Test Engine Compression (1993-2003 3.9L Dodge Dakota).
• How To Test For A Blown Head Gasket (1993-2003 3.9L Dodge Dakota).
• Engine Management Sensor Circuit Diagram (1994-1995 3.9L V6 Dodge Dakota).