How To Test The GM MAF Sensor (3.1L, 3.4L, 4.3L, 5.0L And 5.7L)

TEST 2: Testing The Power Circuit

The next thing that needs to be done (when TEST 1 confirms the MAF signal is stuck in one value), is check that the MAF sensor is receiving 10 to 12 Volts.

To check for the presence of these 12 Volts, we'll do a simple multimeter voltage test on the wire I've labeled with the letter C (see the photo above).

IMPORTANT: Be careful when probing the front of the female terminals of the connector. The multimeter lead could damage the terminal if you use to much pressure.

OK, these are the test steps:

1. 1

   Place your multimeter's dial in Volts DC mode.

2. 2

   Disconnect the MAF sensor connector from its electrical connector.

3. 3

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

4. 4

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

5. 5

   Turn the key ON but don't crank or start the engine.

6. 6

   You should see 10 to 12 Volts on the multimeter.

Let's take a look at your test results:

CASE 1: Your multimeter registered 10 to 12 Volts. This is the correct result and tells you that the MAF sensor is getting power.

Your next step is to make sure the MAF sensor has Ground, for this next test go to: TEST 3: Testing The 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 on your multimeter, then this exonerates the MAF sensor as bad since without this voltage it's not gonna' work.

Your next step is to repair/restore this power circuit. Once this power circuit has been restored to the MAF sensor, it should start working again.

TEST 3: Testing The Ground Circuit

So far your testing of the MAF sensor has confirmed that:

• The MAF sensor signal is stuck in one value (TEST 1).
• The MAF sensor is getting power (TEST 2).

The next test step is to make sure the MAF sensor is getting a good Ground (since without Ground it won't work).

Like the previous voltage test you just performed, this a very easy multimeter test too.

Alright, this is what you need to do:

1. 1

   Place your multimeter's dial in Volts DC mode.

2. 2

   Disconnect the MAF sensor connector from its electrical connector.

3. 3

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

4. 4

   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 (see the photo above).

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 result confirms that the MAF sensor is getting a good Ground.

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

• The MAF sensor signal is stuck in one value (TEST 1).
• The MAF sensor is getting power (TEST 2).
• In this test section, you've confirmed that it's getting Ground.

CASE 2: Your multimeter DID NOT register 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. Without a good path to Ground, it's not gonna' work.

Your next step is to repair/restore this Ground circuit. Once this Ground circuit has been restored to the MAF sensor, it should start working again.