TEST 1: Testing The Power Circuit For 12 Volts

How To Test The MAF Sensor (GM 4.8L, 5.3L, 6.0L, 8.1L) How To Test The MAF Sensor (GM 4.8L, 5.3L, 6.0L, 8.1L)

OK, the very first thing that you'll need to do is to make sure the mass air flow (MAF) sensor is getting power (12 Volts). You can use a test light or a multimeter. The following test steps assume that you're using a multimeter.

By the way, I recommend that you test the circuit with the connector connected to the mass air flow (MAF) sensor and using a wire piercing probe (or any other apropriate tool) to pierce the wire (to get to the Signal). Probing the front of the terminal, to get to the 12 Volt Signal, could lead to some major complications. OK, nuff said, here's the test:

  1. Place the multimeter in Volts DC mode.
  2. Connect the RED multimeter lead to the PINK wire identified with the number 4 (see image viewer photos) using an appropriate tool.
  3. Connect the BLACK lead of the multimeter to a good ground point on the engine or to the battery negative terminal.
  4. Turn the key to the ON position and observe the voltage value the multimeter registers.
  5. The multimeter should register between 10 to 12 Volts DC.

Let's take a look at what your test results mean:

CASE 1: The multimeter registered 10 to 12 Volts DC (or the if the test light came on), then this indicates that the MAF sensor is getting juice (12 Volts). The next step is to verify that it's also getting a good ground, go to TEST 2.

CASE 2: The multimeter DID NOT register 10 to 12 Volts DC (or the if the test light DID NOT come on), this exonerates the MAF sensor as being BAD, since without 12 Volts, the MAF sensor will not work and this will light up the CHECK ENGINE LIGHT (CEL) on your instrument cluster. Repairing the cause of the missing voltage will solve the problem.

TEST 2: Testing The Ground Circuit

How To Test The MAF Sensor (GM 4.8L, 5.3L, 6.0L, 8.1L) How To Test The MAF Sensor (GM 4.8L, 5.3L, 6.0L, 8.1L)

Testing the ground circuit follows pretty much the same procedure as the test steps for testing the power circuit. Here are the steps:

  1. Place the multimeter in Volts DC mode.
  2. Connect the BLACK multimeter lead to the BLACK (or BLACK with WHITE stripe) wire identified with the number 3 (see image viewer photos) using an appropriate tool.
  3. Connect the RED lead of the multimeter to the battery positive terminal.
  4. Turn the key to the ON position and observe the voltage value the multimeter registers.
  5. The multimeter should register between 10 to 12 Volts DC.

Let's take a look at what your test results mean:

CASE 1: The multimeter registered 10 to 12 Volts DC (or the if the test light came on), then this indicates that the MAF sensor has a good ground. The next step is to verify that the MAF sensor is creating a good MAF Signal based on the airflow the engine is breathing, go to TEST 3.

CASE 2: The multimeter DID NOT register 10 to 12 Volts DC (or the if the test light DID NOT come on), this exonerates the MAF sensor as being BAD, since without a good ground, the MAF sensor will not work and this will light up the CHECK ENGINE LIGHT (CEL) on your instrument cluster. Repairing the cause of the missing voltage will solve the problem.

TEST 3: Testing The MAF Signal Circuit

Before you jump into this last test, let's go over some basic working theory of how the mass air flow (MAF) sensor works that'll help you to breeze thru' it.

The MAF sensor's job is to measure the amount of air the engine is breathing at any given RPM and to convert this measurement into a Hertz frequency reading (as measured by a digital multimeter that can read Hz frequency) the PCM can use to calculate fuel injection. Therefore the more air the engine breathes, the higher the Hertz frequency that the MAF sensor will output to the PCM.

So keeping this in mind, the Hertz frequency reading will be higher at 2500 RPM's than at 800 RPM's. On your multimeter, this Hertz (Hz) reading will progress in a smooth way as you accelerate the engine and decrease in the same way as the engine decelerates. Now, in testing the MAF sensor, you won't be looking for a specific Hertz (Hz) 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. OK, crash course is over, let's start testing.

How To Test The MAF Sensor (GM 4.8L, 5.3L, 6.0L, 8.1L) How To Test The MAF Sensor (GM 4.8L, 5.3L, 6.0L, 8.1L)

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

The MAF sensor must be connected to its connector to perform this test.

  1. With the key in the OFF position.
  2. With a suitable tool connected to the RED multimeter lead, probe the wire identified with the number 5.
  3. Put the multimeter in Hertz frequency (Hz) mode (don't have a digital multimeter that can read Hertz frequency? Click here to see my recommendations: Buying A Digital Multimeter For Automotive Diagnostic Testing).
  4. Connect the BLACK lead to the battery (-) negative terminal.
  5. Start the already warmed up engine.
  6. Note the Hertz 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. Manually accelerate the engine from the engine compartment as you watch the multimeter's frequency readings. The Hertz frequency readings should increase.
  8. When you let go off of the throttle and the engine returns to idle, the Hertz reading should come down to the base Hertz reading you observed in step 6 of this test.
  9. Repeat this as often as you need to verify that the Hertz numbers on the multimeter rise and decrease smoothly every single time.
  10. If the MAF sensor is working correctly, the readings on your multimeter will not spike up and down crazily but will increase smoothly as you manually accelerate the engine and decrease smoothly as you let the engine return to idle.

Let's take a look at what your test results mean:


CASE 1: If the Hertz (Hz) signal rose smoothly and decreased smoothly as the engine was accelerated and decelerated respectively, then this indicates that the mass air flow (MAF) sensor is working correctly.

CASE 2: If the Hertz (Hz) signal DID NOT rise smoothly nor decreased smoothly as the engine was accelerated and decelerated respectively, then this indicates that the mass air flow (MAF) sensor is BAD. Replace it.