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.
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:
- 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.