How To Test The MAP Sensor (1992-1996 3.9L Dodge Ram Pickup/Van)

TEST 2: Making Sure The MAP Sensor Is Getting Power

If in TEST 1 the MAP sensor did not produce a decreasing/increasing voltage signal as you applied/released vacuum, then there's a good chance it might not be receiving 5 Volts from the fuel injection computer.

The wire we need to check for these 5 Volts is the violet with white stripe VIO/WHT wire of the MAP sensor connector.

NOTE: Be careful when probing the front of the MAP sensor connector to test for this voltage since you could permanently damage the female metal terminal. I recommend that you back-probe the connector with a back probe or use a wire-piercing probe.

OK, 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

   Connect the red multimeter test lead to the VIO/WHT wire of the MAP sensor harness connector
   
   This is the wire that connects to the terminal labeled with the number 3 in the image above.

4. 4

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

5. 5

   Have a helper turn the key to the On position, but don't crank or start the engine after the multimeter test leads have been set up.

6. 6

   Your multimeter should register 4.5 to 5 Volts DC if the VIO/WHT wire is feeding the manifold absolute pressure (MAP) sensor with power.

Let's examine your test result:

CASE 1: The VIO/WHT wire has power (4.5 to 5 Volts). This is the correct and expected test result and lets you know that your Dodge Ram pickup/van's manifold absolute pressure (MAP) sensor is getting power.

Your next step is to make sure that the MAP sensor is getting Ground on the BLK/LT BLU (black w/ light blue) wire. For this test, go to: TEST 3: Making Sure The MAP Sensor Is Getting Ground.

CASE 2: The VIO/WHT wire DOES NOT have power (4.5 to 5 Volts). Check that the key is in the on position and that you're testing the correct wire and re-test.

If your multimeter still shows that the VIO/WHT wire DOES NOT have power, then you've found the reason why the MAP sensor did not create a voltage signal in TEST 1.

Although it's beyond the scope of this tutorial to find the reason why these 5 Volts are missing, you'll need to get yourself a wiring diagram (for your particular Dodge Ram pickup/van) and check the continuity of this wire between the MAP sensor and the PCM.

TEST 3: Making Sure The MAP Sensor Is Getting Ground

The previous MAP sensor tests have confirmed that:

• The MAP sensor IS NOT creating an increasing/decreasing throttle plate voltage signal on the DK GRN/RED wire (TEST 1).
• The VIO/WHT wire is providing the MAP sensor with 5 Volts DC (TEST 2).

The last test is to make sure that the black with light blue stripe (BLK/LT BLU) wire is feeding the MAP sensor with Ground.

NOTE: Be careful and do not short this wire to battery voltage, or you'll fry your Dodge pickup/van's fuel injection computer. The multimeter voltage test described in the test instructions is a safe way to check for the presence of Ground in the BLK/LT BLU 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

   Connect the black multimeter test lead to the BLK/LT BLU wire of the MAP sensor harness connector
   
   This is the wire that connects to the terminal labeled with the number 1 in the image above.

4. 4

   Connect the red multimeter test lead directly on the battery's positive (+) terminal.

5. 5

   Have a helper turn the key to the On position, but don't crank or start the engine after the multimeter test leads have been set up.

6. 6

   Your multimeter should register 10 to 12 Volts DC if the BLK/LT BLU wire is feeding the MAP sensor with Ground.

Let's interpret your test results:

CASE 1: The multimeter registered 10 to 12 Volts DC. This confirms that the MAP sensor is getting Ground from the fuel injection computer.

You can conclude that the manifold absolute pressure sensor is defective (and needs to be replaced) if you have:

1. Confirmed that the MAP sensor is not creating an increasing/decreasing voltage signal (TEST 1).
2. Confirmed that the VIO/WHT wire is providing 5 Volts DC (TEST 2).
3. Confirmed that the BLK/LT BLU wire is providing Ground (TEST 3).

If you'd like to save a few bucks on the MAP sensor, check out the section: Where To Buy The MAP Sensor And Save.

CASE 2: The multimeter DID NOT register 10 to 12 Volts DC. Re-check all of your test connections and repeat the test.

If the multimeter still does not show the indicated voltage, then you've found the reason why the MAP sensor did not create a decreasing/increasing voltage signal in TEST 1.

Although it's beyond the scope of this tutorial to find the reason why this Ground is missing, you'll need to get yourself a wiring diagram (for your particular Dodge Ram pickup/van) and check the continuity of this wire between the MAP sensor and the PCM.

More 3.9L V6 Dodge Tutorials

I've written quite a few 3.9L V6 Dodge ‘how to’ tutorials that may help you troubleshoot the issues on your Dodge van, pick up or SUV. You can find all in these two indexes:

• 3.9L Dodge Index Of Articles.
• 3.9L, 5.2L, 5.9L Dodge Index Of Articles.

Here's a small sample of the articles/tutorials you'll find in the indexes:

• How To Test A No Start Condition (Dodge 3.9L, 5.2L, 5.9L).
• How To Diagnose Misfire Codes (Dodge 3.9L, 5.2L, 5.9L).
• How To Test The Fuel Injectors (Dodge 3.9L, 5.2L, 5.9L).
• How To Test The Ignition Coil -No Start Tests (Chrysler 3.9L, 5.2L, 5.9L).
• How To Test The MAP Sensor (P0107, P0108) (Dodge 3.9L, 5.2L, 5.9L).