How To Test The Ford MAF Sensor (4.2L, 4.6L, 5.4L)

Testing the MAF (Mass Air Flow) sensor on your Ford truck or SUV or full size van is a very simple and easy affair. This article will walk you through the whole process without removing the MAF sensor from the engine. As you may already know, the MAF sensor is inside the round air filter canister assembly and this article will teach you how to test it.

The MAF sensor test/diagnostic can be accomplished in four easy steps using a multimeter. You don't even need a scan tool! Below you'll find important pre-test info that'll speed up the diagnostic process.

If you're looking for the article on how to test the Ford MAF sensor that's not inside the air filter canister assembly, go here: How To Test Ford MAF Sensors Using A Multimeter.

OK, one last thing before we jump into the test, if you're diagnosing a 4.6L or 5.4L pick up or SUV, let me just make you aware where you can find a complete list of 4.6L and 5.4L 'How To Test' articles that are located in this Web Site and at and this list is found here: Ford 4.6L, 5.4L Index Of Articles.

In Spanish You can find this tutorial in Spanish here: Cómo Probar El MAF Ford (4.2L, 4.6L, 5.4L) (at:

Common Symptoms Of A Bad Ford MAF Sensor

This list covers 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.
    • P0102: Mass Air Flow (MAF) Circuit Low Input.
    • P0103: Mass Air Flow (MAF) Circuit High Input.
  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 My Ford MAF Sensor Just Dirty?

Is My Ford MAF Sensor Just Dirty? How To Test The Ford MAF Sensor (4.2L, 4.6L, 5.4L)

MAF sensors have a tremendous tendency to get dirty and cause several headaches that may include: bad gas mileage, higher emissions, and/or lack of power. For the most part, when one is dirty, the truck, or van or SUV seems to drive OK, but not with the same peppiness as before. So how do I diagnose a dirty/contaminated Ford MAF sensor? Well:

  1. I'll take a quick look before I start my diagnostic and see if the two hot-wires (that make up the MAF sensor) are dirty. By dirty I mean 'contaminated' (to use an industry standard term). To see an example of this: 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.

Why does it get dirty/contaminated? Well, it's usually due to an air filter not performing its job or the round plastic canister assembly, that holds the air filter, is broken or not sealing correctly. The Ford MAF sensors are some of the easiest MAF sensor to clean. To see/read the step by step instructions on how to clean this type of Ford MAF sensor in the round air filter canister, click here: Cleaning The Ford Canister Type MAF Sensor.

Checking The MAF Sensor Hot-Wires For Contamination. How To Test The Ford MAF Sensor (4.2L, 4.6L, 5.4L)

Air Leaks Wreaking Havoc On MAF Sensor Control

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 rubber air ducts that connect the MAF sensor to the throttle body to see if it's loose or disconnected.

Circuit Descriptions Of The Ford MAF Sensor's Connector

Circuit Descriptions Of The Ford MAF Sensor's Connector. How To Test The Ford MAF Sensor (4.2L, 4.6L, 5.4L)

Whether your driving a Ford, Mercury or Lincoln full size pick up (F150-F350), SUV, or full size van (E150-E350) the circuits descriptions of the wires coming out of the round air filter canister are the same. You'll notice that the photos (in the image photo above) have the MAF connectors numbered 1 thru' 4. I'll be using these numbers for the circuit descriptions. Here's the description of each circuit below:

  • Number 1:
    • MAF Signal.
  • Number 2:
    • Ground that the ECM provides.
  • Number 3:
    • Ground.
  • Number 4:
    • 12 Volts.

To test these circuits you'll need to use a tool to pierce the wire to be tested. I recommend using a wire-piercing probe since it'll be the most effective and easiest way of getting to the signal. 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(s). Take all safety precautions.

Another important thing to note is that the color of the wires (coming out of your Ford, Lincoln or Mercury pick up or SUV or van) 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.

Ford Vehicles:

  • Expedition 4.6L, 5.4L
    • 1997, 1998, 1999, 2000, 2001, 2002
  • Excursion 4.6L, 5.4L
    • 1997, 1998, 1999, 2000, 2001, 2002
  • E150, E250, E350 4.2L, 4.6L, 5.4L
    • 1997, 1998, 1999, 2000, 2001, 2002

Ford Vehicle:

  • F150, F250, F350 4.2L, 4.6L, 5.4L
    • 1997, 1998, 1999, 2000, 2001, 2002

Lincoln Vehicle:

  • Navigator 4.6L, 5.4L
    • 1997, 1998, 1999, 2000, 2001, 2002, 2003