Mass Air Flow (MAF) Sensor Test 2.4L Nissan D21 Hard Body (1990-1995)

TEST 2: Testing The MAF Sensor Ground Circuit

The MAF is getting power (according to the result of the previous test), so now you need to verify that its also has a good path to Ground.

The circuit (wire) that provides this path to Ground is the wire labeled with the letter C in the photo above.

To check for Ground, we'll do a simple multimeter voltage test with the multimeter in Volts DC mode.

Alright, let's get going:

1. 1

   Place your multimeter in Volts DC mode and disconnect the MAF sensor from its electrical connector.

2. 2

   Probe the MAF sensor wire, that's identified with the letter C in the photo, with the black multimeter test lead.

3. 3

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

4. 4

   Your multimeter should display 10 to 12 Volts DC if the MAF sensor is getting Ground.

Let's find out what your test results mean:

CASE 1: Your multimeter registered 10 to 12 Volts. This result indicates that the D21's MAF sensor has a good Ground circuit.

The next step is to test the MAF signal, go to: TEST 3: Testing The MAF Signal.

CASE 2: Your multimeter DID NOT register 10 to 12 Volts. Recheck all of your multimeter connections and try the test again. If still no voltage, then this result exonerates the D21's MAF sensor as the cause of the MAF code lighting up your check engine light (CEL) or MAF issue, since without this Ground, the MAF sensor will not produce a signal to the computer.

Finding and repairing the cause of this missing Ground will resolve the MAF sensor issue with your Nissan D21 pickup.

TEST 3: Testing The MAF Signal

Now, for the last test that will either confirm that the mass air flow sensor is bad or not, on your D21 pickup.

What we're gonna' do is rev the engine up and down to see if the MAF signal voltage increases and decreases.

If the MAF sensor is defective, you'll see that the MAF signal voltage will stay stuck in one single value as you accelerate/decelerate the engine.

By the way, to get the best test result, perform this test with a warmed up engine.

IMPORTANT: The MAF sensor must be connected to its connector to perform this test. You'll need to use a back probe or a wire piercing probe to access the MAF signal within the wire. You can see an example of this tool here: Wire Piercing Probe.

These are the test steps:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

   Probe the MAF sensor wire that is identified with the letter B in the photo with the red multimeter test lead.
   
   Connect the black multimeter test lead to the battery negative (-) terminal.

3. 3

   Start the already warmed up engine.

4. 4

   Note the Volts DC reading on your multimeter as the engine idles. 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 voltage reading.

5. 5

   Manually accelerate the engine as you observe how the multimeter's voltage value increases.
   
   The higher you accelerate the engine, the higher the voltage reading on your multimeter.

6. 6

   Let the engine returns to idle, the voltage value on the multimeter should return to the base voltage value you recorded in step 5. This voltage reading may not be the exact same but should be very close.

7. 7

   Repeat this as often as you need to verify that the Volt numbers on the multimeter rise/decrease as you rev up/down the engine.

Let's interpret your multimeter test result:

CASE 1: The voltage reading increased and decreased smoothly as you revved up/down the engine. This is the correct test result and let's you know that your Nissan D21's MAF sensor is working correctly.

If the MAF sensor were defective, it would have stayed stuck producing a single voltage value as you revved up/down the engine.

CASE 2: The voltage reading DID NOT increase and decrease smoothly according to the amount you accelerated or decelerated the engine, then the mass air flow sensor on your Nissan D21 is bad. Replace the MAF sensor.