TEST 3: Testing The MAF Signal
Now for the test you signed up for!... You're now gonna' see if the MAF sensor is actually measuring the incoming airflow (with your multimeter of course).
Start the engine and let it reach it's normal operating temperature, since it's important to perform this test with a warm engine. You'll be using the DC voltage reading you'll obtain at idle as a base value to diagnose the MAF sensor.
The MAF sensor must be connected to its connector to perform this test.
Probe the MAF sensor wire that is identified with the letter C with the red multimeter test lead. This will be the red wire in the photo above.
Place the multimeter in Volts DC mode.
Connect the black multimeter test lead to the battery negative (-) terminal.
Start the already warmed up engine.
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.
Manually accelerate the engine. The multimeter's voltage value should increase.
The higher you accelerate the engine, the higher the voltage reading on your multimeter.
Let the engine return 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.
The voltage should increase and decrease as you accelerate and decelerate the engine.
If the MAF sensor is defective, the MAF voltage signal will stay fixed in one single value no matter how much you accelerate the engine.
Let's interpret your MAF signal test result:
CASE 1: If the voltage reading increased and decreased smoothly according to the amount of acceleration you caused, then the MAF sensor is working correctly.
CASE 2: If 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 2.4L Frontier (2.4L Xterra) is bad. Replace the MAF sensor.
Where To Buy The MAF Sensor And Save $$$$
You can buy the 2.4L Nissan Frontier (2.4L Xterra) Mass Air Flow (MAF) Sensor at your local autoparts. I know that Auto Zone sells it, but depending on which one you want to buy, it will either cost you US$390 or US$415 (as of this writing) and this is EXPENSIVE!!!
Another option you may want to explore is buying this bad boy online and saving a lot of money. Below, you'll find two links (to the same place) so that you can shop and compare and see what option is best for you! By the way, the Hitachi MAF0110 maf sensor is the original equipment sensor:
NOTE: Not sure if the mass air flow (MAF) sensor fits your particular vehicle? Don't worry. Once you get to the site they'll ask you for the particulars of your vehicle and they'll check it fits. If it doesn't fit, they'll find you the right one.
If this info really saved the day, buy me a beer!