How To Test The MDP Sensor With A Multimeter (2.4L Mitsubishi Eclipse, Expo, Galant)

In this tutorial, I'll show you how to test the manifold differential pressure (MDP) sensor on your 2.4L equipped Mitsubishi Galant (Eclipse or Expo) using a simple multimeter.

NOTE: The manifold pressure differential (MDP) sensor is usually mistaken for a MAP sensor. Although they both function in the exact same manner the MPD sensor is not used to help calculate air flow (for fuel injection purposes). The MDP sensor is used as a feedback sensor for the EGR system.

You can find this tutorial in Spanish here: Cómo Probar El Sensor De la Presión Diferencial Del Múltiple (2.4L Mitsubishi) (at:

Symptoms Of A BAD MDP Sensor

Your Mitsubishi's 2.4L engine's fuel system is not a speed density type where the PCM relies on a manifold absolute pressure (MAP) sensor to help calculate the amount of air entering the engine (it uses the MAF sensor for air flow measurement). Rather, the main purpose of the manifold differential pressure (MDP) sensor is to monitor the exhaust gas recirculation (EGR) valve.

Keeping the above in mind, manifold differential pressure (MDP) sensor issues are usually accompanied by EGR system problems (but not always).

The most obvious symptom of a failed MDP sensor is the check engine light (CEL) will be shining nice and bright. If your PCM is doing its job, you'll have a specific MDP sensor trouble code stored in its memory (which you can retrieve with a scan tool or code reader).

Here's a list of the symptoms you'll see with a failed MDP sensor:

  1. Diagnostic trouble codes (DTCs):
    1. P01400: Manifold Differential Pressure Sensor Circuit Failure.
    2. P0400 EGR Valve Flow Failure.
  2. Doesn't pass the smog check.

Let's jump into the first test in the next subheading...

TEST 1: Checking The MDP Sensor Signal

How To Test The MDP Sensor With A Multimeter (2.4L Mitsubishi Eclipse, Expo, Galant)

In this first test, we're gonna' check to see if the MDP sensor is creating a proper voltage signal when we manually apply vacuum to it.

This is pretty easy test, but it does require that you apply vacuum to the MDP sensor. You can use a vacuum pump or you can use your mouth.

NOTE: The ignition key must be in the On position and MDP sensor must remain connected to its connector during this test.

OK, to get this show on the road, this is what you need to do:

  1. 1

    Remove the MDP sensor from its place on the intake manifold.

  2. 2

    Connect your vacuum pump to the MDP sensor's vacuum port using a vacuum hose. Before you proceed to the next step, make sure the MDP sensor is connected to its connector.

  3. 3

    With your multimeter in Volts DC mode probe the wire that connects to the MDP sensor connector terminal labeled with the number 1 (in the illustration above).

    You'll need to use a tool like a wire piercing probe to access the signal inside the wire. To see what a wire piercing probe looks like, go here: Wire Piercing Probe.

  4. 4

    Ground the black multimeter test lead directly on the battery negative terminal.

  5. 5

    Turn the Key on but don't start the engine.

  6. 6

    Your multimeter should register about 3.8 to 4.0 Volts DC.

    Now, pump the vacuum pump to apply vacuum to the MDP sensor. The voltage should drop down to 1.1 Volts.

    As you release the vacuum you're applying to the MDP sensor, the voltage should increase back to the value you noticed at the beginning.

  7. 7

    Repeat this test step several times and each time, you should see the same values on your multimeter.

OK, let's take a look at what your vacuum pump test results mean:

CASE 1: Your multimeter registered the indicated voltages as you applied vacuum. This tells you that the manifold differential pressure sensor is OK (not defective).

Now, if your vehicle still has the MDP sensor code lighting up the check engine on your instrument cluster.. take a look at the section: MDP Code Won't Go Away for more info.

CASE 2: Your multimeter registered voltage, but it did not increase or decrease as you applied vacuum. This confirms that the manifold differential pressure (MDP) sensor on your Mitsubishi is bad. Replacing the MDP sensor will solve the MDP sensor trouble code lighting up the check engine light.

CASE 3: Your multimeter registered 0 Volts. This usually means that the MDP sensor is fried. To be absolutely sure, I suggest confirming that the MDP sensor has power and Ground. If both (power and Ground) are present, the MDP sensor is bad. To test for power, go to TEST 2: Verifying The Manifold Differential Pressure Sensor Is Getting Power.