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!
Contents of this tutorial:
- Common Symptoms Of A Bad Ford MAF Sensor.
- Is The MAF Sensor Just Dirty?
- Air Leaks.
- MAF Sensor Circuit Descriptions.
- Summary Of The MAF Sensor Tests.
- MAF TEST 1: Testing The Power Circuit.
- MAF TEST 2: Testing The Ground Circuit.
- MAF TEST 3: Testing The 2nd Ground Circuit.
- MAF TEST 4: Testing The MAF Signal.
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:
- MAF Codes that light up the check engine light (CEL) on your instrument cluster.
- P0102 MAF Signal Low Input to PCM.
- P0103 MAF Signal High Input to PCM.
- P1100 MAF Circuit Intermittent Voltage Input.
- P1101 MAF Sensor Circuit Output Voltage low During KOEO Self Test.
- MAF sensor malfunction that DOES NOT light up the check engine light (CEL).
- Lean and/or Rich code(s).
- Fuel Trim code(s).
- A tremendous lack of power upon acceleration.
- Black smoke coming from the tail-pipe.
- Bad gas mileage.
- 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:
- 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).
- Or, I'll test it first following the guidelines set in this article, to see if it's producing a MAF signal.
- 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.
- 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.
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
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.
Photo 1 of 2, in the image viewer, is that of a 4 wire MAF sensor. This is a non intake air temp (IAT) sensor MAF sensor.
Photo 2 of 2 is of a MAF with 6 wires, since it has the IAT sensor integrated with the assembly.
You'll notice that the photos (in the image viewer) 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:
- Letter F:
- Intake air temperature (IAT) sensor circuit (not applicable if you have a 4 wire MAF sensor).
- Letter D:
- MAF Signal.
- Letter C:
- Ground that the ECM provides.
- Letter B:
- Letter A:
- 12 Volts.
- Letter E:
- 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.
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.