TEST 1: Testing The Power (12 V) Circuit

Making Sure That The MAF Sensor Is Getting Power. Mass Air Flow (MAF) Sensor Test Nissan Sentra 1.6L (1995-1999)

Unlike many of the MAF sensors out there, the 1995, 1996, 1997, 1998, 1999 Nissan Sentra 1.6L mass Air Flow (MAF) sensor uses only three wires to perform its magic. In this section we'll test each one to see if the right signal is present.

The very first thing that we'll do is check that the MAF sensor is receiving 12 volts.

The wire that feeds these 12 Volts is the one labeled with the number 3 in the phot above.

Let's get started:

  1. Put the multimeter in VOLTS DC mode.
  2. Disconnect the MAF sensor connector from the MAF sensor.
  3. With the RED multimeter test lead and an appropriate tool, probe the MAF sensor wire labeled with the number 3 shown in the photo above.
  4. With the BLACK lead of the multimeter probe battery (-) negative terminal.
  5. Turn the key on but don't crank or start the engine.

You should see 12 Volts on the multimeter. Do you have 12 volts?

CASE 1: The multimeter registered 12 Volts -All is good in the neighborhood, GO TO TEST 2.

CASE 2: The multimeter DID NOT register 12 Volts -The MAF sensor is not the problem. Without this voltage the MAF sensor will not work.

TEST 2: Testing The Ground Circuit

Making Sure That The MAF Sensor Is Getting Ground. Mass Air Flow (MAF) Sensor Test Nissan Sentra 1.6L (1995-1999)

In the previous test we checked that the sensor was receiving 12 Volts. Now we'll check that the MAF sensor is getting a good ground. This ground is provided by the ECM internally.

The wire that supplies ground to the MAF sensor is the one labeled with the number 2 in the photo above.

Be careful and take extreme care not to short-circuit this wire to ground or power as you're probing it.

You can test this circuit with the connector connected to MAF sensor or not.

  1. Turn key to the OFF Position.
  2. Put the multimeter in VOLTS DC mode.
  3. Connect the BLACK multimeter test lead to the wire labeled with the number 2 in the photo above.
  4. Connect RED lead to the battery (+) positive terminal.
  5. Turn the ignition switch to the RUN position.

You should see a voltage of 12 Volts. Do you have that?


CASE 1: The multimeter registered 12 Volts -All is good in the neighborhood, GO TO TEST 3.

CASE 2: The multimeter DID NOT register 12 Volts -The MAF sensor is not the problem. Without this ground the MAF sensor will not work.

TEST 3: The MAF Signal

Testing The MAF Signal With A Multimeter. Mass Air Flow (MAF) Sensor Test Nissan Sentra 1.6L (1995-1999)

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

Start the engine and let it reach it's normal operating temperature. You'll be using the voltage reading you will obtain at idle as a base to diagnose the MAF sensor.

As mentioned at the beginning of this tutorial, the MAF signal reacts to amount of air the engine is breathing. So if you accelerate the engine, the MAF sensor signal voltage will increase.

If the MAF sensor is bad on your Nissan Sentra, the voltage reading will stay stuck in one value no matter how much you accelerate the engine.

IMPORTANT: The MAF sensor must be connected to its connector to perform this test. So you'll need to use a back-probe or a wire piercing probe to access the signal inside the wire. To see an example of a wire piercing probe, check this link out: Wire Piercing Probe.

These are the test steps:

  1. With the key in the OFF position.
  2. With a suitable tool connected to the RED multimeter lead, probe the wire labeled with the number 1 shown in the photo.
  3. Put the multimeter in VOLTS DC mode.
  4. Connect the BLACK lead to the battery (-) negative terminal.
  5. Start the already warmed up engine.
  6. Note the Volts 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.
  7. Accelerate the engine as you watch the multimeter's voltage readings.
  8. The voltage numbers should correspond to the amount of acceleration.
  9. Repeat this as often as you need to verify that the voltage numbers on the multimeter rise smoothly every single time.
  10. If the MAF sensor is good, these readings will not spike up and down crazily but will correspond to the amount of air the engine is breathing at the different RPMs you're accelerating the engine to.

Did the signal rise smoothly with each increase in engine acceleration and stay steady at idle?

CASE 1: If the MAF signal rose smoothly and fell smoothly according to the engine's RPM's, then the MAF is ok. In other words, the MAF sensor is creating a MAF signal and IS NOT defective.

CASE 2: If the MAF signal DID NOT rise smoothly or fall smoothly according to the engine's RPM's or if there was no MAF signal at all, then the MAF sensor is BAD.

Here's the reason why:

  1. You have confirmed that the MAF sensor is getting power (TEST 1).
  2. You have confirmed that the MAF sensor is getting ground (TEST 2).
  3. In this test step, you have confirmed that the MAF sensor is NOT creating a voltage signal that increases with higher engine RPMs and decreases when the engine returns to idle.

Taking the above into account, you can conclude that the MAF sensor is bad and needs to be replaced.

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