How To Test The MAP Sensor (1996-1999 2.5L OHV Dodge Dakota)

TEST 2: Verifying MAP Sensor Has 5 Volts And Ground

Now that you have confirmed that a MAP sensor signal isn't decreasing as you apply vacuum (TEST 1), you need to make sure that it's getting power and Ground.

Both of these are provided by your Dodge Dakota's fuel injection computer.

OK, for specifics: We're gonna' test the violet with white stripe (VIO/WHT) wire for 5 Volts. We're gonna make sure that the black with light blue stripe (BLK/LT BLU) wire is providing Ground.

IMPORTANT: When testing the Ground wire of the MAP sensor connector, be careful not to short it to 12 Volts (battery power) or you will fry your 2.5L Dodge Dakota's fuel injection computer.

Set your multimeter to Volts DC and:

1. 1

   Verify that the VIO/WHT wire has voltage (4.5 to 5 Volts DC) with the key on but engine off.
   
   Connect the red multimeter test lead (using the appropriate tool) to the VIO/WHT wire. Connect the black multimeter test lead to the negative battery terminal.
   
   Your multimeter should read 4.5 to 5 Volts DC.

2. 2

   Verify that the BLK/LT BLU wire has Ground with the key on but engine off.
   
   Connect the black multimeter test lead (using the appropriate tool) to the BLK/LT BLU wire. Connect the red multimeter test lead to the positive battery terminal.
   
   Your multimeter should read 12 Volts DC.

Let's take a look at your test results:

CASE 1: The MAP sensor is getting power and Ground. This is the correct and expected test result.

With this test result you can now conclude that the MAP sensor is defective and that it needs to be replaced. To be a bit more specific, you can reach this conclusion because you have confirmed that the MAP sensor is getting power and Ground and yet it's not producing a decreasing/increasing voltage signal when you applied vacuum (in TEST 1).

CASE 2: The MAP sensor IS NOT getting power or Ground. This test result tells you that the reason the map voltage signal did not react to the vacuum you applied (in TEST 1) is because it's missing power and/or Ground.

The most common cause of this test result is a problem in the wiring between the MAP sensor connector and the fuel injection computer connector. Although it's beyond the scope of this tutorial to check the MAP sensor wiring, your next steps should be to check the continuity of the MAP sensor circuits between its connector and the fuel injection computer connector.

MAP Sensor Trouble Code Doesn't Go Away

Having a MAP sensor trouble code that won't go away can be frustrating. I've seen this happen a few times and in this section I'm gonna' offer you some testing suggestions that have helped me to nail the problem on the head.

It's been my experience that 4 things are usually behind a MAP sensor trouble code that won't go away and these are:

• Engine compression problems.
• MAP sensor connector wiring problems (between MAP sensor and the fuel injection computer connector).
• Air/fuel mixture problems caused by a fuel pump that is dying a slow death but is able to start and keep the engine running.
• Defective fuel injection computer.

These are the test steps I take when I've come across this problem:

1. Check fuel pressure and make sure it's within specification.
2. Check engine compression and make sure that all cylinders are producing enough compression.
3. Check ignition timing with a timing light.
4. Check for vacuum leaks around the intake manifold gasket.
5. Check that the MAP sensor wires (between the MAP sensor and fuel injection computer) for open-circuits and short-circuits (short-circuit to each other, or Ground, or power).
6. Check that any fuel injection input sensor that shares the power and Ground circuit, with the MAP sensor, is not fried and causing the MAP sensor from getting power or Ground.

In the few cases that I have diagnosed a defective computer, I made sure that the MAP sensor itself was good. Eliminated the fuel pump and engine compression as the cause of the problem. I then tested the wiring between the MAP sensor and the computer with a wiring diagram. I also made sure that any other input sensor that shares Ground and power with the MAP sensor was not defective (sensors that share power and Ground with the MAP sensor are: TPS, CKP and CMP sensors, etc.).

Once I had eliminated all of the above, then I could confidently conclude that the PCM was defective.

More 2.5L Dodge Dakota Tutorials

You can find a complete list of tutorials here: Chrysler 2.5L 4-Cylinder Index Of Articles.

Here's a sample of the tutorials you'll find there:

• How To Test For A Blown Head Gasket (1993-2002 2.5L Dodge Dakota).
• How To Test The TPS (1996-1999 2.5L OHV Dodge Dakota).
• How To Test Engine Compression (1993-2002 2.5L Dodge Dakota).
• Oxygen Sensor Heater Test -P0141 (1996-1997 2.5L Dodge Dakota).