How To Test The Ford Mass Air Flow (MAF) Sensor

Testing the Ford mass air flow (MAF) sensor on all of the Ford, Lincoln and Mercury cars and trucks is a very simple test that can be done without a scan tool. All you need is a multimeter. I recommend using a digital multimeter but an analog multimeter can also be used.

Ford has used a Hot-Wire type mass air flow sensor for many years that either comes with or without an internal air temperature sensor. If the MAF sensor has 6 wires, then this is a dead giveaway that it has the air temp sensor integrated inside. If the Ford MAF sensor on your car has 4 wires, then it does not have an air temp sensor integrated within it (the air temp sensor will be somewhere on the air duct that connects the MAF sensor to the throttle body or somewhere on the intake manifold.

NOTE: There are several different Ford MAF sensors types. These come in either a black or light gray body and with 6 or 4 wires in the connector. Regardless of what color body the MAF sensor has or the amount of wires in the connector... they are all tested in the same way!

En Español You can find this tutorial in Spanish here: Cómo Probar el Sensor de Flujo de Aire (Sensor MAF) de Ford (at: autotecnico-online.com).

If your Ford or Mercury vehicle uses the MAF sensor in the round Canister Air Filter assembly, go here: Ford MAF in Round Canister Air Filter assembly.

Common Symptoms Of A BAD Ford MAF Sensor

This is not the most definitive list on the subject, but does cover the majority of symptoms I've seen on these types of Ford mass air flow sensors:

  1. MAF Codes that light up the CHECK ENGINE LIGHT (CEL) on your instrument cluster.
    1. P0102  MAF Signal Low Input to PCM.
    2. P0103  MAF Signal High Input to PCM.
    3. P1100  MAF Circuit Intermittent Voltage Input.
    4. P1101  MAF Sensor Circuit Output Voltage low During KOEO Self Test.
  2. MAF sensor malfunction that DOES NOT light up the CHECK ENGINE LIGHT (CEL).
  3. Lean and/or Rich code(s).
  4. Fuel Trim code(s).
  5. A tremendous lack of power upon acceleration.
  6. Black smoke coming from the tail-pipe.
  7. BAD gas mileage.
  8. Vehicle may idle rough and stall.

Is The MAF Sensor Just Dirty?

The most common fix I've performed on the majority of MAF sensor problems on Fords have been cleaning it. Now, the symptoms that accompany a dirty (contaminated) Ford MAF sensor are not that harsh or noticeable on engine performance (of course this is not an absolute truth).

What I mean is that a dirty MAF sensor doesn't wreak a lot of havoc on the car or truck. Usually the biggest complaints are bad gas mileage and/or a slight lack of power. So how do I diagnose a dirty/contaminated Ford MAF sensor? Well:

  1. I'll remove it (before I start any testing) and eye-ball the two 'hot-wires' to see if they are covered in fuzz or other material (you can see an example of this here: Dirty MAF Sensor Example).
  2. Or, I'll test it first following the guidelines set in this article, to see if it's producing a MAF signal.
  3. If it is producing a signal, but the signal's response is too slow to changes in throttle position, then I know to look into cleaning it.
  4. If you need to clean it, here's the article: How To Clean The Ford Mass Airflow Sensor (at troubleshootmyvehicle.com).

Why does it get dirty/contaminated? Well, this MAF sensor easily becomes contaminated with dirt and stuff from the air filter not performing its job or the box that holds the air filter is broken or not sealing correctly. The Ford MAF sensors are some of the easiest MAF sensor to clean. All it takes is to remove the two torx head screws that hold it in place and spray-clean the two hot-wires with a MAF sensor Cleaner.

Air Leaks

The second most common problem I have encountered on most Fords (Mercurys and Lincolns) over the years is air leaks between the MAF sensor and the throttle body. It is crucial, yes very critical that you first check that there are no air leaks between these two. Air entering after the mass air flow sensor into the engine will negatively impact fuel injection. And will skew the results of your tests which could result in the replacement of a good MAF (and in the process throwing money away).

How do you check for air leaks? With your eyes and hands. That's right, no special tools required. Just eyeball and physically shake/move the ducting to see if it's loose or disconnected.


MAF Sensor Circuit Descriptions

MAF Sensor Circuit Descriptions. How To Test The Ford Mass Air Flow (MAF) Sensor

Whether your Ford, Mercury or Lincoln car has a MAF sensor with 4 or 6 wires (coming out of the connector) their circuits share the circuit descriptions.

In the photo above you can see a 4 wire MAF sensor. This is a non intake air temp (IAT) sensor MAF sensor. The photo below is a MAF with 6 wires, since it has the IAT sensor integrated with the assembly.

You'll notice that the photos (above and below) have the MAF connectors lettered A thru' F (If you look closely at the MAF sensor housing, you'll see these letters on it too). I'll be using these letters for the circuit descriptions.

Here's the description of each circuit below:

  1. Letter F:
    1. Intake air temperature (IAT) sensor circuit (not applicable if you have a 4 wire MAF sensor).
  2. Letter D:
    1. MAF Signal.
  3. Letter C:
    1. Ground that the ECM provides.
  4. Letter B:
    1. Ground.
  5. Letter A:
    1. 12 Volts.
  6. Letter E:
    1. Air Temp. sensor circuit (not applicable if you have a 4 wire MAF sensor).

Using a wire-piercing probe is the most effective and easy way of getting to the MAF signal, since you don't risk damaging the female terminals of the connector by probing them directly. If you need to see what this tool looks like, click here: Wire-Piercing Probe. Independent of the method you use, be careful not to damage the wire or the female terminal. Take all safety precautions.

Another important thing to note is that the color of the wires (coming out of your Ford, Lincoln or Mercury car or truck) does not matter. In other words, the circuit description/job of the wire is the same regardless of Make/Model and color of the wire.

IMPORTANT: All of the tests are ON CAR TESTS, do not remove the mass air flow sensor from the vehicle or from its plumbing.

How To Test The Ford Mass Air Flow (MAF) Sensor

Summary Of The MAF Sensor Tests

OK, you're gonna' start by checking the basics. These are 12 Volts and battery ground to the MAF sensor. After that, we'll test the actual performance of the MAF sensor as the engine is running. Use a digital multimeter for all tests where a multimeter is called for.

The MAF sensor produces an analog voltage signal. This MAF signal's DC voltage is directly related to amount of air the engine is breathing. Therefore, if the engine is breathing in more air at 2500 RPM's that at an idle of 900RPM's the voltage output will be greater at 2500 RPM's than at idle.

Now, when testing this voltage signal, the important thing to know is not an actual volts number at a specific RPM, but to look for crazy and extreme fluctuations in the voltage signal that do not correspond to the actual air intake (RPM's) of the engine or no signal at all. For example: If at Idle the voltage reading starts to spike up and down without you accelerating the engine or if there's no signal at all.

In the TEST 4 section of this article, I'll show how you'll use a base voltage reading at idle from the MAF sensor that will help you to confirm that the MAF sensor is bad or not.


MAF TEST 1: Testing The Power Circuit

Making Sure The MAF Sensor Is Getting Power. How To Test The Ford Mass Air Flow (MAF) Sensor

OK, to get this show on the road and find out if the MAF sensor on your Ford is BAD, we'll test for power first.

I'm gonna' make you a very important recommendation: Don't test the front of the connector to test for this voltage.

What I suggest you to do is to use a test probe that pierces thru' the wire's insulation (Wire Piercing Probe)... again, DO NOT insert anything into the female terminal.

Whatever method you use, the key here is to avoid damaging the MAF connector's female terminal or the wire. OK, this is what you need to do:

  1. 1

    Put the multimeter in VOLTS DC mode. Do not disconnect MAF sensor connector from the MAF sensor.

  2. 2

    With the RED multimeter test lead and an appropriate tool, probe the MAF sensor connector's A circuit as shown in the photo.

  3. 3

    With the BLACK lead of the multimeter probe BATT (-) negative terminal. Turn Key On with the engine Off.

  4. 4

    You should see 12 Volts on the multimeter. Do you have 12 volts?

Let's take a look at what your test results mean:

CASE 1: Your multimeter registered 12 Volts: This is the correct result, the next step is to make sure the MAF sensor has ground, for this, go to: MAF TEST 2: Testing The Ground Circuit.

CASE 2: Your multimeter DID NOT register 12 Volts: Recheck all of your multimeter connections and retest. If you still do not see these 12 Volts... then this exonerates the MAF sensor as BAD, since without this voltage.. it's not gonna' work.

MAF TEST 2: Testing The Ground Circuit

Making Sure The MAF Sensor Is Getting Ground. How To Test The Ford Mass Air Flow (MAF) Sensor

So far we know that the MAF sensor is getting juice (12 Volts). Let's find out if it's getting ground too.

The Ford MAF sensor uses two different ground paths, this one (that you're about to test) is just a power ground and it grounds directly on the engine or battery negative terminal.

Alright, this is what you need to do:

  1. 1

    Put the multimeter in VOLTS DC mode.

  2. 2

    With the BLACK multimeter test lead and an appropriate tool, probe the wire identified with the letter letter B in the photo.

  3. 3

    With the RED lead of the multimeter probe battery positive terminal.

  4. 4

    You should see 12 Volts on the multimeter. Do you have 12 volts?

Let's take a look at what your test results mean:

CASE 1: Your multimeter registered 12 Volts: This is the correct result, the next step is to make sure the MAF sensor has ground, for this, go to: MAF TEST 3: Testing The 2nd Ground Circuit.

CASE 2: Your multimeter DID NOT register 12 Volts: Recheck all of your multimeter connections and retest. If you still do not see these 12 Volts... then this exonerates the MAF sensor as BAD, since without this ground.. it's not gonna' work.


MAF TEST 3: Testing The 2nd Ground Circuit

Making Sure The MAF Sensor Is Getting PCM Ground. How To Test The Ford Mass Air Flow (MAF) Sensor

Now, we'll check the second ground circuit of the MAF sensor. This ground is provided by the ECM internally.

CAUTION: When testing this circuit, you've got to be careful and take extreme care not to short-circuit this wire to power... or you'll fry the Fuel Injection Computer.

OK, this is are the steps:

  1. 1

    Put the multimeter in VOLTS DC mode.

  2. 2

    With the BLACK multimeter test lead and an appropriate tool, probe the wire identified with the letter letter C in the photo.

  3. 3

    With the RED lead of the multimeter probe battery positive terminal.

  4. 4

    You should see 12 Volts on the multimeter. Do you have 12 volts?

Let's take a look at what your test results mean:

CASE 1: Your multimeter registered 12 Volts: This is the correct result, the next step is to make sure the MAF sensor has ground, for this, go to: MAF TEST 4: Testing The MAF Signal.

CASE 2: Your multimeter DID NOT register 12 Volts: Recheck all of your multimeter connections and retest. If you still do not see these 12 Volts... then this exonerates the MAF sensor as BAD, since without this ground.. it's not gonna' work.

MAF TEST 4: Testing The MAF Signal

Testing The MAF Signal. How To Test The Ford Mass Air Flow (MAF) Sensor

Now that you've gotten the power and ground signals out of the way... now you'll test the MAF sensor's signal.

It's important that the engine be at its normal operating temperature. So, start the engine and let it reach it's normal operating temperature.

I know I'm stating the obvious, but the MAF sensor must be connected to its connector to perform this test. OK, let's start:

  1. 1

    With the Key in the Off position, and your multimeter still in Volts DC mode.

  2. 2

    With a suitable tool connected to the RED multimeter lead, probe the wire labeled with the letter D in the photo. Connect the BLACK lead to the battery (-) negative terminal.

  3. 3

    Crank up the engine and get her to idle.

    Once the idle stabilizes, take a look at the voltage number or numbers your multimeter is throwing at you. This voltage may fluctuate a little or a lot, and this is OK. Whatever they're doing... this is your base MAF signal voltage.

  4. 4

    Now, open the throttle (manually) to rev up the engine. As the engine revs up... keep your eyes on the multimeter's voltage numbers. The voltage should increase.

  5. 5

    When you let go off of the throttle and the idle comes back down, the voltage reading should also come down and should hover around the numbers you noticed at the beginning of this test.

  6. 6

    Rev up and let the engine come back down several times. Each time, the voltage numbers on your multimeter should rise and fall smoothly.

  7. 7

    If the MAF sensor is good, the voltage numbers on the multimeter should rise and fall smoothly and without gaps. If the MAF sensor is BAD, you see one of three things: 1.) you WON'T see a voltage registered on the multimeter at all or 2.) the voltage will stay stuck in one number or 3.) the voltage numbers will spike up and down crazily even when you're not accelerating the engine.

Did the signal rise smoothly with each increase in engine acceleration and stay steady at idle?.Let's take a look at what your test results mean:

CASE 1: The voltage numbers rose and fell smoothly and without gaps: This tells you that the MAF sensor is good and not the cause of the MAF issue or Diagnostic Trouble Code.

CASE 2: The multimeter registered 0 Volts or a voltage that was erratic: Recheck all of your multimeter connections and retest. If you still do not see the indicated voltage rising and falling smoothly, then the mass air flow (MAF) sensor is BAD. Replace the MAF sensor.

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