How To Test The Vane Air Flow Sensor (VAF) F2 & F2T engine 2.2L

[1stgenWizard]

Symptoms Of A Defective VAF Sensor

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The most common symptoms of a defective vane air flow sensor Sensor are:

• A MAF Sensor code.
  A tremendous lack of power upon acceleration.
  Black smoke coming from the tail-pipe.
  Vehicle may idle rough and stall.

The VAF sensor test is easy but there are a couple of things that have to be done first. The two most important are:

Verify that the engine does not have any vacuum leaks.
Verify that there are no ignition system misfires. A misfire condition will skew the results of the test you'll perform here.
If the above conditions exist, repairing them first will more than likely solve your vehicle's drive-ability issue without having to test the VAF sensor, if not continue with the VAF test in this article.

VAF Sensor Test Basics
OK, we're gonna' start by checking the basics. These are 12 Volts and Ground to the vane air flow sensor. After that, we'll test the actual performance of the VAF sensor.

I recommend using a digital multimeter for all tests where a multimeter is called for. Why? -you may ask. Only a digital multimeter will be able to keep up with and register the voltage output signal of the VAF sensor.

This voltage signal is directly related to amount of air the engine is breathing. Common sense tells us that the engine will breathe in more air at 2500 RPMs than at an idle of 900 RPMs.

So keeping this in mind, the voltage value on the multimeter will be greater at 2500 RPMs than at 900 RPMs

Now, when testing this voltage output signal, the important thing to know is not an actual voltage 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. For example: If at Idle the voltage reading starts to spike up and down without you accelerating the engine.

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

VAF Sensor Circuit Descriptions

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The safest way to test these circuits, and the method I always use, is using a wire piercing probe (you can see an example here: Wire Piercing Probe). Using this probe, I don't have to disconnect the VAF sensor's connector to probe the front of the female terminal and possibly risk damaging it.

Independent of the method you use, be careful not to damage the wire or the female terminal. Take all safety precautions.

IMPORTANT: All of the tests are ON CAR TESTS, do not remove the vane air flow sensor from the vehicle or from its plumbing (all of the figures show the VAF sensor off of the vehicle just for illustration purposes only).

You'll notice that in the photo above, the VAF sensor's connector is numbered 1 thru 7. The only circuits that we are going to be concerned about in this tutorial are circuits 3, 4, and 6. Here's the description of each circuit below.

• Number 1- Fuel pump switch circuit.
  Number 2- Fuel pump switch circuit.
  Number 3- Sensor Ground thru' the ECM.
  Number 4- 12 Volts.
  Number 5- 9 Volts.
  Number 6- VAF signal.
  Number 7- Air Temperature Sensor Circuit.

We're ready to get started...

[1stgenWizard]

TEST 1: Making Sure The VAF Sensor Is Getting Power

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The very first thing that we'll do is check that the vane air flow sensor is receiving 12 Volts.

The wire that feeds power to your Mazda's vane air flow meter is the one labeled with the number 4 in the photo above.

OK, let's get started:

• 1
  Place your multimeter in Volts DC mode and disconnect VAF sensor from its electrical connector.
  
  2
  With the red multimeter test lead and an appropriate tool, probe the VAF sensor Connector's Number 4 circuit as shown in the photo. This is the red with black stripe wire.
  
  3
  With the black multimeter test lead probe the battery negative (-) terminal.
  
  4
  Turn Key On but don't crank or start your Mazda's engine.

Let's interpret your voltage test result:
CASE 1: Your multimeter registered 10 to 12 Volts DC. This is the correct test result.

Your next step is to make sure your Mazda's vane air flow sensor is getting Ground. For this test go to: TEST 2: Making Sure The VAF Sensor Is Getting Ground.

CASE 2: Your multimeter DID NOT register 10 to 12 Volts DC. Without power, the VAF sensor on your Mazda 626 will not function.

Your next step is to find out why this power is missing and restore it. This will get the VAF sensor back on its feet.

TEST 2: Making Sure The VAF Sensor Is Getting Ground

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In the previous test we checked that the VAF sensor was receiving 12 Volts.

Now we'll check that the VAF sensor is getting a good Ground.

This Ground is fed to the sensor via the wire identified with the number 3 in the photo above.

IMPORTANT: Be careful and take all necessary safety precautions not to short this Ground wire to battery voltage (12 Volts). This Ground is provided thru' the fuel injection computer itself.

Let's start:

• 1
  Place your multimeter in Volts DC mode.
  
  2
  Connect the black multimeter test lead to the number 3 wire shown in the photo above.
  
  This is the light green with yellow stripe wire of the connector.
  
  3
  Connect red multimeter test lead to the battery positive (+) terminal.
  
  4
  10 to 12 Volts should be present with the Key On or Off since this Ground is a chassis Ground.

Let's interpret your voltage test result:

CASE 1: Your multimeter registered 10 to 12 Volts DC. This is the correct test result.

Now that you've confirmed that the VAF sensor is getting power and Ground, the next (and last) step is to test the vane air flow sensor's signal. For this test go to: TEST 3: Testing The VAF Signal With A Multimeter.

CASE 2: Your multimeter DID NOT register 10 to 12 Volts DC. Without Ground, the VAF sensor on your Mazda 626 will not function.

Your next step is to find out why this Ground is missing and restore it.
This will get the VAF sensor back on its feet.

[1stgenWizard]

TEST 3: Testing The VAF Signal With A Multimeter

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Now that the basics have been checked, we'll check the VAF signal coming out of the sensor and going to the ECM.

There are two methods to test the vane air flow sensor on your 1988-1992 2.2L Mazda 626.

The method in this test section is the one that I recommend since it's the most accurate way of testing the VAF meter.

The other method is to test the sensor dynamically (with the engine running) and you can find that test in TEST 4.

In this test section we're gonna' manually actuate the VAF sensor's measuring plate (vane) while we test the continuity of two specific terminals (on the sensor itself).

If the VAF sensor is good, then your multimeter should register an Ohms value that will smoothly increase as you open the measuring plate and decrease as you close it.

These are the test steps:

• 1
  Disconnect the vane air flow sensor's connector.
  
  2
  Place the multimeter in Ohms (Ω) mode.
  
  3
  Connect the multimeter leads (with a suitable tool) to the male spade terminals of the sensor that correspond to: Circuit Number 3 and Circuit Number 6.
  
  4
  Manually open and close the sensor's measuring plate (vane) as you watch the Ohms readings on the multimeter.
  
  5
  The range of the resistance (Ω) will be anywhere in the vicinity of 20 Ohms with the plate fully closed to 1000 Ohms with the plate fully open.
  
  6
  Repeat this as often as you need to verify that the numbers on the multimeter decrease or rise smoothly every single time and without any gaps.

Let's interpret your multimeter test result:

CASE 1: The Ohms value increased/decreased as you opened/closed the measuring plate (vane) and without gaps (in the reading). This is the correct test result.

You can conclude that your 1988-1992 2.2L Mazda 626's VAF sensor is NOT defective if you have confirmed it's getting power, Ground, and that the Ohms value increased/decreased as indicated in this test section.

CASE 2: The Ohms value DID NOT increase/decrease as you opened/closed the measuring plate (vane) as indicated in the test instructions. This test result tells you that the VAF sensor is defective.

TEST 4: Testing The VAF Signal With The Engine Running

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In this test section we're gonna' see if the VAF sensor is creating a voltage signal that increases as we rev the engine up.

It's important that before you start the test, the engine in your Mazda should be at its normal operating temperature. You'll be using the voltage reading you'll obtain at idle as a base to diagnose the VAF sensor.

If the VAF sensor is defective, it will produce a voltage signal that'll stay stuck in one value as you rev the engine up or a value that increases but has gaps.

IMPORTANT: The VAF sensor must remain connected to its electrical connector to perform this test. For this reason you'll need to use a back probe or a wire-piercing probe. You can see an example of this tool here: Wire Piercing Probe.

OK, let's get started:

• 1
  Connect the red multimeter test lead to the Number 6 wire as shown in the photo. This is the red with black stripe wire.
  
  2
  Place the multimeter in Volts DC mode and connect the black multimeter test lead to the battery negative (-) terminal.
  
  3
  Start the already warmed up engine.
  
  4
  Note the voltage reading on your multimeter at idle. This reading may be stable (with only small fluctuations) or unstable with very extreme fluctuations. No matter what the instability in the reading, this will be your base reading.
  
  5
  Accelerate the engine as you watch the multimeter's voltage readings.
  
  This voltage should INCREASE every time the engine is accelerated.
  
  6
  Repeat this as often as you need to verify that the voltage numbers on the multimeter INCREASE smoothly every single time.

If the VAF sensor is good, the voltage reading will increase/decrease as you rev up/rev down the engine.

Let's analyze your VAF signal test result:
CASE 1: The voltage signal increase/decrease as you accelerated/decelerated the engine. This is the correct test result and let's you know that the vane air flow meter is working OK.

CASE 2: The voltage signal DID NOT increase/decrease as you accelerated/decelerated the engine. This test result let's you know that the vane air flow meter is defective.