How To Test The Mass Air Flow Sensor (1999, 2000 1.8L Mazda Protegé)

Testing the mass airflow sensor on your 1.8L Mazda Protegé involves three simple tests. These three tests can be performed with a simple multimeter. That's right, you don't need an expensive scan tool to do it.

To be a bit more specific, these three tests involve making sure the mass airflow sensor is producing a signal, that it's getting power, and that it's getting ground.

I'll show you how to do these 3 tests in a step-by-step manner in this tutorial.

Contents of this tutorial at a quick glance:

  1. Symptoms Of A BAD MAF Sensor.
  2. What Tools Do I Need To Test The MAF Sensor?
  3. What Does The MAF Sensor Do?
  4. TEST 1: Checking The MAF Sensor Signal.
  5. TEST 2: Makign Sure The MAF Sensor Is Getting Power And Ground.
  6. Where To Buy The MAF Sensor And Save.

Symptoms Of A BAD MAF Sensor

One of several important information inputs, that your Protegé's fuel injection computer needs, is the amount of air that is entering the engine.

This makes it possible for the computer to know how much fuel to inject into each cylinder. This makes the mass air flow sensor a critical component of your Mazda Protegé's engine management system. So when it fails engine performance suffers, not too mention that you'll have the check engine light shining nice and bright (with a MAF sensor trouble code).

The failed MAF sensor will also caused one or several of the following symptoms:

  1. Diagnostic trouble codes:
    1. P0101: Mass Air Flow (MAF) Sensor System Performance
    2. P0102: Mass Air Flow (MAF) Sensor Circuit Low Input.
    3. P0103: Mass Air Flow (MAF) Sensor Circuit High Input.
  2. BAD gas mileage.
  3. Rough idle.
  4. Lack of power on acceleration.
  5. Black smoke coming out of the tailpipe.
  6. Won't pass the emissions test.

It's rare for the mass air flow (MAF) sensor to go BAD and not leave a diagnostic trouble code... but sometimes you'll get the MAF trouble code and the MAF is good. So, it's always a good idea to test it.

What Tools Do I Need To Test The MAF Sensor?

The cool thing about testing the MAF sensor on your Mazda is that you don't need any expensive or exotic tools. Here's a basic list of tools you'll need:

  1. A multimeter.
    1. If you need to upgrade or buy a multimeter, check out my recommendation: Abe's Multimeter Recommendation (found at: easyautodiagnostics.com).
  2. Wire piercing probe.
    1. Although this tool is not an absolute must, if you do buy one, you'll realize just how easy it makes testing the voltages inside the wires.
    2. If you need to see what this tool looks like, you can see it here: Wire Piercing Probe.

A scan tool comes in handy... but you won't need it to use the testing info in this article.

What Does The MAF Sensor Do?

How To Test The Mass Air Flow Sensor (1999, 2000 1.8L Mazda Protegé)

In this section I am going to explain how the mass air flow (MAF) sensor works in very simple terms. This information will help you to understand the ‘how’ and ’why’ of the mass air flow sensor test I'm gonna' show you in this tutorial

In a nutshell: The mass airflow sensor's function is to measure the amount of air that is entering the engine at any given RPM. Your 1.8L Mazda Protegé's fuel injection computer then uses this measurement (of air flow) to inject the correct amount of fuel.

To get into more specifics: As the air enters and passes the MAF sensor, the sensor creates a voltage signal that increases with increased air flow (as you accelerate the engine) or decreases as the engine breathes less air.

What will help us to test the MAF sensor and find out if it's good or bad is knowing that the more air the engine breathes, the bigger the voltage signal the MAF sensor creates. The less air the engine breathes, the smaller the voltage signal the MAF sensor sends the PCM.

Here's what it looks like on a multimeter:

  1. At an idle under 1000 RPM's the MAF sensor outputs about 1.1 Volts DC.
  2. At about 1500 RPM's the math signal output is about 1.2 volts DC.
  3. Ask about 3000 RPM's the MAF signal output is about 1.7 volts DC.

Remember, the important thing to know, is that at higher RPMs, when the engine is breathing more air, the MAF signal (in voltage) is greater than when the engine is idling.

Now, in testing the MAF sensor, you won't be looking for a specific voltage number at a specific RPM... but for crazy fluctuations in the signal that don't correspond to the amount of air entering the engine or NO SIGNAL AT ALL.

These are the circuit descriptions of the mass air flow (MAF) sensor

MAF Sensor Connector Pin Out
Pin Wire Color Description
1 Black w/ Red (BLK/RED) stripe Ground.
2 Light Green w/ Black (LT GRN/BLK) stripe MAF Sensor Signal Output.
3 White w/ Red (WHT/RED) stripe Power (12 Volts).


NOTE: There's a good chance that the color of the wires on your 1.8L Mazda Protegé are not the same as the ones listed above. This shouldn't worry you because if the MAF sensor and the connector are the same as the one that's in the photo above, then the circuit descriptions are the same.

Let's turn the page and get testing...