How To Test The MAF Sensor (1996 3.1L V6 Buick Century)

The mass airflow (MAF) sensor on the 1996 3.1L V6 Buick Century can easily be tested with a multimeter capable of measuring Hertz frequency (if you don't have one, I'll show you where you can buy one).

In this tutorial, I'm going to show you how to perform the three tests you need to find out if the MAF sensor is good or bad. We'll make sure it's producing a MAF signal the PCM can use, and we'll also make sure it's getting both power and Ground.

You'll find all of the test steps explained in a step-by-step manner so that you can quickly and easily find out if the MAF sensor is toast and needs to be replaced, or if the issue lies somewhere else.

APPLIES TO: This tutorial applies to the following vehicles:

• 3.1L V6 Buick Century: 1996.

If all you need to do is clean the MAF sensor, take a look at this tutorial: How To Clean The MAF Sensor (GM 3.3L 3.8L).

MAF SENSOR TESTS 1994-1995 AND 1997-2005:

• How To Test The MAF Sensor (1994-1995 3.1L V6 Buick Century)..
• How To Test The MAF Sensor (1997-2005 3.1L V6 Buick Century).

Common Symptoms Of A Bad MAF Sensor

The MAF sensor on your Buick Century is a critical engine management component. Its job is to measure the amount of air entering the engine as it runs.

With the information provided by the MAF sensor, the PCM can now calculate the correct amount of fuel to inject into the engine.

So, when this bad boy fails, you're definitely going to notice engine performance issues. Depending on how it failed, you'll see one or more of the following symptoms:

• Check engine light ON: The check engine light is illuminated on the instrument cluster.
• MAF sensor trouble code: The PCM has stored a MAF sensor diagnostic trouble code in its memory.
• Lack of power: The engine feels sluggish or hesitates when you accelerate.
• Black smoke from the tailpipe: The engine is running excessively rich, causing black exhaust smoke.
• Poor fuel economy: Your Buick starts using noticeably more fuel than normal.
• Rough idle: The engine idles unevenly or feels like it's about to stall.
• Starts then stalls: The engine starts but dies almost immediately afterward.
• Hard starting: The engine has to crank longer than normal before it finally starts.

Circuit Descriptions Of The MAF Sensor Connector

The MAF sensor on your Buick Century is a three-wire sensor. Each wire (or circuit) is labeled with the letter A, B, or C.

One wire carries the MAF sensor signal, another supplies power, and the remaining wire provides Ground.

In the table below is a brief description of what each wire does, information that's going to help us in the diagnostic tests I've laid out in this tutorial.

Terminal	Wire Color	Circuit Function
A	Yellow (YEL)	MAF Signal Output To PCM
B	Black with white stripe (BLK/WHT)	Chassis Ground
C	Pink (PNK)	12 Volts From The ECM (15A) Fuse

IMPORTANT: All of the tests are ON CAR TESTS, do not remove the mass air flow sensor from the vehicle or from its plumbing.

How Does The MAF Sensor Work?

The MAF (Mass Air Flow) sensor's job is to keep track of the amount of air entering the engine. The PCM relies on this information to calculate how much fuel to inject, whether the engine is idling, cruising down the highway, or you're stepping on the gas.

Inside the MAF sensor are two heated sensing wires. As air flows across them, it cools them off. The greater the amount of air entering the engine, the greater the cooling effect.

The MAF sensor monitors this cooling effect and converts it into a digital frequency signal that's measured in Hertz (Hz), which it then sends to the PCM.

The good news is that you don't need an expensive scan tool to test this signal. If your multimeter can measure Hertz frequency, you've got everything you need to check whether the MAF sensor is doing its job or not.

As more air enters the engine, the MAF sensor's Hertz value should increase. As airflow decreases, the Hertz reading should decrease too.

So, when you accelerate the engine, you should see the frequency reading climb. When the engine settles back down to idle, the frequency should drop accordingly.

If the frequency stays fixed at one value regardless of engine speed or how far you open the throttle, that's a strong indication that the MAF sensor is toast.

TEST 1: Testing The MAF Signal With A Multimeter

To get our MAF sensor diagnostic started, we're going to connect our multimeter to the MAF signal wire and check the sensor's output as we rev up and rev down the engine.

Remember:

• As you accelerate the engine, the Hertz reading should increase.
• As you let off the throttle, the Hertz reading should decrease.

Like I mentioned earlier, the most common failure of the MAF sensor is that its signal output stays stuck at one value regardless of airflow.

You'll need a multimeter that can read Hertz frequency to check the MAF sensor's signal output. If you don't have one or need to upgrade yours, this is the one I recommend: Tekpower TP8268 AC/DC Auto/Manual Range Digital Multimeter (Amazon affiliate link)

IMPORTANT: To check the MAF sensor's output signal, it has to remain connected to its 3-wire connector. So, you'll need to use either a back probe on the connector or a wire-piercing probe on the wire. This is the tool that I use, which works both as a back probe and a wire-piercing probe: Goupchn 4mm Banana to Banana Plug Test Leads Kit (Amazon affiliate link).

CAUTION: The engine must be running during this test. Keep your hands, clothing, and test leads away from any moving engine parts. Always think safety first.

Follow these test steps:

1. 1

   Set your multimeter to read Hertz (Hz) frequency.

2. 2

   Connect the black multimeter lead to the battery negative (-) terminal.

3. 3

   Back probe terminal A (YEL wire) with the red multimeter lead, or use a wire-piercing probe to access the circuit while leaving the MAF sensor connected.

4. 4

   Start the engine and let it idle. If possible, perform this test with the engine at normal operating temperature.

5. 5

   Observe the frequency reading with the engine idling.
   
   The reading may be very steady or it may fluctuate slightly. Either condition is normal. This will be your idle (base) reading.

6. 6

   From the engine compartment, manually open the throttle while watching the multimeter.
   
   As engine speed increases, the frequency reading should increase too.

7. 7

   Release the throttle and let the engine return to idle.
   
   The frequency should decrease and return to approximately the same idle reading you noted in step 5.

8. 8

   Repeat the acceleration test several times.
   
   Every time you open and release the throttle, the frequency should increase and decrease smoothly as engine airflow changes.

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

CASE 1: The Hertz (Hz) reading increased as you accelerated the engine and decreased as you let off the throttle. This is the correct test result and tells us that the MAF sensor is responding to changes in engine airflow just like it should. In other words, it's working correctly.

CASE 2: The Hertz (Hz) reading stayed fixed at one value as you accelerated the engine and let off the throttle. This isn't the correct test result and is usually a strong indication that the MAF sensor is defective.

Before we condemn the MAF sensor and replace it, however, we need to make sure it's getting both power and Ground. The next thing we're gonna do is verify that it's receiving 12 Volts. Go to: TEST 2: Making Sure The MAF Sensor Is Getting 12 Volts.

TEST 2: Making Sure The MAF Sensor Is Getting 12 Volts

If the MAF sensor didn't produce a Hertz (Hz) signal that increased and decreased as you accelerated and let off the throttle, the next thing we need to do is make sure it's getting power.

The MAF sensor receives battery power from the ECM (15A) fuse located in the dash fuse box. We're going to verify that this power supply is present with a simple multimeter voltage test.

On the 1996 3.1L Buick Century, this power is delivered through the pink (PNK) wire, which connects to terminal C of the MAF sensor's connector.

If your multimeter registers 10 to 12 Volts, then we can rule out a power supply problem and move on to the last test.

This is what you need to do:

1. 1

   Disconnect the MAF sensor from its electrical connector.

2. 2

   Set your multimeter to Volts DC mode.

3. 3

   Connect the black multimeter lead to the battery negative (-) terminal.

4. 4

   Turn the ignition key to the ON position, but don't crank or start the engine.

5. 5

   Touch the red multimeter lead to the front of terminal C (PNK wire) on the MAF sensor connector.
   
   CAUTION: Probe the terminal carefully to avoid spreading or damaging the female terminal.

6. 6

   Your multimeter should read 10 to 12 Volts DC.

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

CASE 1: Your multimeter registered 10 to 12 Volts. This is the correct test result and tells us that the MAF sensor is getting the power it needs to operate.

The next thing we need to do is make sure it's getting Ground. Go to: TEST 3: Making Sure The MAF Sensor Is Getting Ground.

CASE 2: Your multimeter did NOT register 10 to 12 Volts. Without this voltage, the MAF sensor cannot produce a MAF signal.

Your next step is to find out why this power is missing. Start by checking the ECM (15A) fuse and repairing the open-circuit or power supply problem before replacing the MAF sensor.

Once power has been restored to the circuit, the MAF sensor should start working again (assuming no other problems are present).

TEST 3: Making Sure The MAF Sensor Is Getting Ground

Up to this point in your MAF sensor diagnostic, you've confirmed the following:

• TEST 1: The MAF signal is either missing or stuck at one value regardless of engine speed (airflow).
• TEST 2: The MAF sensor is getting 10 to 12 Volts.

For our final diagnostic test, we're going to make sure that the MAF sensor is getting the Ground it needs to operate and create the signal the PCM needs to see.

This Ground is supplied through terminal B of the MAF sensor's connector. Terminal B corresponds to the black with white stripe (BLK/WHT) wire of the sensor's 3-wire connector.

Since this is a chassis Ground, it's available at all times regardless of whether the key is in the ON or OFF position.

To check this circuit, we'll perform a simple multimeter voltage test. If Ground is present, we'll have all the information we need to figure out whether the MAF sensor is defective or if something else is causing the problem.

Let's get started:

1. 1

   Disconnect the MAF sensor from its electrical connector.

2. 2

   Set your multimeter to Volts DC mode.

3. 3

   Connect the red multimeter lead to the battery positive (+) terminal.

4. 4

   Touch the black multimeter lead to the front of terminal B (BLK/WHT wire) on the MAF sensor connector.
   
   CAUTION: Probe the terminal carefully to avoid spreading or damaging the female terminal.

5. 5

   Your multimeter should read 10 to 12 Volts DC.
   
   NOTE: This is a chassis Ground and is available at all times regardless of key position.

Let's interpret your test results:

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

CASE 1: Your multimeter registered 10 to 12 Volts. This is the correct test result and tells us that the MAF sensor has a good Ground.

If you've confirmed all three of the following conditions, then you can conclude that the MAF sensor is defective and needs to be replaced:

• TEST 1: The MAF sensor's Hertz (Hz) signal stayed fixed at one value or was missing altogether regardless of engine speed (airflow).
• TEST 2: The MAF sensor was receiving 10 to 12 Volts on its power circuit.
• TEST 3: The MAF sensor has a good Ground on its Ground circuit.

When all three test results match the conditions above, you can confidently rule out an issue with the MAF sensor's power and Ground circuits and conclude that the MAF sensor itself has failed.

CASE 2: Your multimeter did NOT register 10 to 12 Volts. This test result tells us that the MAF sensor isn't receiving Ground. Without a good Ground, it won't be able to produce the signal the PCM needs to see.

Your next step is to find out why this Ground is missing, repair the problem, and then repeat the test.

Once Ground has been restored to the circuit, the MAF sensor should start working again (assuming no other problems are present).

More 3.1L V6 Buick Century Diagnostic Tutorials

You can find a complete list of 3.1L V6 Buick Century tutorials and wiring diagrams in this index:

• 3.1L V6 Buick Century Index of Articles.

Here's a small sample of the tutorials you'll find in the index:

• How To Test An Engine No-Start (1994-2005 3.1L V6 Buick Century).
• How To Troubleshoot A Cylinder Misfire (1994-2005 3.1L V6 Buick Century).
• How To Test The Fuel Injectors (1994-1999 3.1L V6 Buick Century).
• How To Test The Ignition Control Module (1994-2005 3.1L V6 Buick Century).