How To Test The Ford Mass Air Flow (MAF) Sensor

MAF TEST 2: Testing The Power Circuit

For our second test, we'll check that the MAF sensor is getting 10 to 12 Volts.

The wire that supplies this voltage is the red wire labeled with the letter A in the photo above.

NOTE: When probing the female terminal of the connector with the multimeter probe, be careful not to the female terminal or the wire.

OK, this is what you need to do:

1. 1

   Disconnect the MAF sensor from its electrical connector.

2. 2

   Place your multimeter in Volts DC mode.

3. 3

   With the red multimeter test lead and an appropriate tool, gently probe the female terminal that connects to the wire labeled with the letter A in the photo above.

4. 4

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

5. 5

   Turn Key ON with the engine OFF.

6. 6

   You should see 10 to 12 Volts on the multimeter.

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

CASE 1: Your multimeter registered 10 to 12 Volts. This is the correct result. The next step is to make sure the MAF sensor has Ground. To do this, go to: MAF TEST 3: Testing The Chassis Ground Circuit.

CASE 2: Your multimeter DID NOT read 10 to 12 volts. Double check all your multimeter connections and test again.

If you still don't see these 10 to 12 volts, the MAF sensor itself is not bad, as it won't work without that voltage.

MAF TEST 3: Testing The Chassis Ground Circuit

So far we know that the MAF sensor is getting juice (10 to 12 Volts). Let's find out if it's getting Ground too.

The Ford MAF sensor uses two different Ground paths, this one (that you're about to test) is just a chassis Ground and it connects directly on the engine or battery negative terminal.

Alright, this is what you need to do:

1. 1

   Disconnect the MAF sensor from its electrical connector.

2. 2

   Place your multimeter in Volts DC mode.

3. 3

   With the black multimeter test lead and an appropriate tool, gently probe the female terminal that connects to the wire labeled with the letter B in the photo above.

4. 4

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

5. 5

   You should see 10 to 12 Volts on the multimeter.

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

CASE 1: Your multimeter registered 10 to 12 Volts. This is the correct result, the next step is to make sure the MAF sensor has Ground, for this, go to: MAF TEST 4: Testing The 2nd Ground Circuit.

CASE 2: Your multimeter DID NOT register 10 to 12 Volts. Recheck all of your multimeter connections and retest. If you still do not see these 12 Volts, then this exonerates the MAF sensor as bad since without this Ground it's not gonna' work.

MAF TEST 4: Testing The 2nd Ground Circuit

Now, we'll check the second Ground circuit of the MAF sensor. This Ground is provided internally by the fuel injection computer.

CAUTION: When testing this circuit, you've got to be careful not to connect this wire to battery 12 Volts or you'll fry the fuel injection computer. The multimeter test I'm suggesting below is a safe way to test for the presence of Ground in the wire.

OK, this is are the steps:

1. 1

   Disconnect the MAF sensor from its electrical connector.

2. 2

   Place your multimeter in Volts DC mode.

3. 3

   With the black multimeter test lead and an appropriate tool, gently probe the female terminal that connects to the wire labeled with the letter C in the photo above.

4. 4

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

5. 5

   You should see 10 to 12 Volts on the multimeter.

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

CASE 1: Your multimeter registered 10 to 12 Volts. This is the correct result and confirms that the fuel injection computer is providing Ground to the MAF sensor.

You can conclude that the MAF sensor is bad and needs to be replaced if you have:

• Confirmed that the MAF voltage signal does not increase/decrease as you accelerate/decelerate the engine (TEST 1).
• Confirmed the MAF sensor is getting 10 to 12 Volts DC (TEST 2).
• Confirmed the MAF sensor is getting chassis Ground (TEST 3).
• Confirmed the MAF sensor is getting sensor Ground from the computer (this test section).

CASE 2: Your multimeter DID NOT register 10 to 12 Volts. Recheck all of your multimeter connections and retest. If you still do not see these 12 Volts, then this exonerates the MAF sensor as bad since without this Ground it's not gonna' work.