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

In this tutorial, I'll show you how to test the mass airflow (MAF) sensor with nothing more than a multimeter that can read Hertz (Hz).

We'll go through three simple tests that'll help you determine whether the MAF sensor is working correctly or if it's failed.

Each test is explained step by step, so you can follow along even if you've never tested a MAF sensor before.

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).

NOTE: These are all on-car tests, so there's no need to remove the MAF sensor from the engine to check it.

APPLIES TO: This tutorial applies to the following vehicles:

• 3.1L V6 Buick Century: 1994, 1995.

MAF SENSOR CIRCUIT WIRING DIAGRAM:

• MAF Sensor Circuit Wiring Diagram (1994-1995 3.1L V6 Buick Century).

Common Symptoms Of A Bad MAF Sensor

When the MAF sensor starts to fail, it'll usually cause one or more noticeable driveability problems. Depending on how it's failed, you may notice any 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

Before we jump into the tests, it's a good idea to know what each wire on the MAF sensor connector does.

The photos in the image viewer identify the connector terminals as A, B, and C. If you look closely at the connector itself, you'll find these same terminal letters molded into the plastic. I'll be referring to these terminal letters throughout the rest of this tutorial.

If you'd like to see the complete wiring diagram before getting started, check out this article: MAF Sensor Wiring Diagram (1994-1995 3.1L V6 Buick Century).

Here's what each of the three circuits does:

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.

Where To Buy The MAF Sensor And Save

The following links will help you to comparison shop for a known automotive name-brand MAF sensor (no knock-offs) for your 3.1L V6 Buick Century:

How Does The MAF Sensor Work?

The MAF (Mass Air Flow) sensor's job is to measure how much air the engine is drawing in. The PCM uses this information to calculate how much fuel the engine needs under every driving condition.

Inside the MAF sensor are two heated wires. As air flows across them, it cools them down. The more air the engine pulls in, the more cooling takes place.

The sensor converts this information into a digital frequency (Hertz) signal and sends it to the PCM.

The nice thing is that we don't need an expensive scan tool to verify that this signal is changing correctly. As long as your multimeter can measure Hertz (Hz), you can check the MAF sensor's output yourself.

As engine airflow increases, the MAF sensor's Hertz signal should increase too. As airflow decreases, the Hertz reading should decrease.

In other words, when you accelerate the engine, you should see the frequency go up. When the engine returns to idle, the frequency should drop back down.

If the frequency stays stuck at the same value no matter how much you open the throttle, that's a strong indication that the MAF sensor has failed.

TEST 1: Testing The MAF Signal With A Multimeter

Our first test is to check that the MAF sensor is producing a Hertz (Hz) signal that changes as engine airflow changes.

As you accelerate the engine, the Hertz reading should increase. As the engine returns to idle, the Hertz reading should decrease. If it doesn't, we'll have our first clue that the MAF sensor may be bad.

You'll need a multimeter that can measure Hertz (Hz) frequency for this test. If you don't have one, check out my recommendations here: Tekpower TP8268 AC/DC Auto/Manual Range Digital Multimeter (Amazon affiliate link)

IMPORTANT: Leave the MAF sensor connected to its electrical connector while performing this test. To measure the signal, you'll need to back probe the connector or use a wire-piercing probe on the signal wire. You can see an example of this tool here: 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 interpret your test results:

CASE 1: The Hertz (Hz) reading increased and decreased as you accelerated and released the throttle. This is the correct test result and tells you that the MAF sensor is responding to changes in engine airflow. In other words, the MAF sensor is working properly.

CASE 2: The Hertz (Hz) reading stayed the same as you accelerated and released the throttle. This is not the correct test result and usually indicates that the MAF sensor has failed.

Before condemning the MAF sensor, however, we need to make sure it's receiving both power and Ground. The next step is to verify that it's getting 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 with engine speed, our next step is to make sure it's getting power.

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

On the 1994-1995 3.1L Buick Century, this voltage is supplied through the pink (PNK) wire, which is terminal C of the MAF sensor connector.

If you measure 10 to 12 Volts on this circuit, then we can rule out a power supply problem and move on to the final 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 interpret your test results:

CASE 1: Your multimeter registered 10 to 12 Volts. This is the correct test result and confirms that the MAF sensor's power circuit is working properly.

Now we need to verify the Ground circuit. 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 supply, the MAF sensor cannot produce a MAF signal.

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

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

TEST 3: Making Sure The MAF Sensor Is Getting Ground

Now that we've verified the MAF sensor is receiving power, our final electrical test is to make sure it has a good Ground.

The Ground circuit is provided through terminal B of the MAF sensor connector, which is the black with white stripe (BLK/WHT) wire. This is a chassis Ground that's available at all times.

We'll check this circuit with a simple multimeter voltage test. If the Ground circuit checks out, we'll have everything we need to determine whether the MAF sensor itself is bad 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:

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

You can confidently conclude that the MAF sensor is bad if all three of the following conditions are true:

• TEST 1: The MAF sensor's Hertz (Hz) signal did not increase and decrease as engine speed changed.
• TEST 2: The MAF sensor was receiving 10 to 12 Volts on the power circuit.
• TEST 3: The MAF sensor has a good Ground on the Ground circuit.

When all three test results match the conditions above, you can conclude that the MAF sensor has failed and needs to be replaced.

CASE 2: Your multimeter DID NOT register 10 to 12 Volts. This tells you the MAF sensor isn't receiving Ground. Without a good Ground, the sensor cannot operate.

Your next step is to find out why the Ground circuit is open or has excessive resistance, repair the problem, and then repeat the test.

Once the Ground has been restored, the MAF sensor should begin working again (assuming no other faults 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).