This article will help you to diagnose the mass air flow (MAF) sensor on any 2000, 2001, 2002 Nissan Sentra (with a 1.8L engine) using only a multimeter.
This is a simple multimeter test that's done in Volts DC mode. No Scan Tool's required or any other expensive testing equipment.
To help you navigate this article a little easier, here are its contents at a glance:
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar El Sensor MAF De 2000-2002 Nissan Sentra 1.8L (at: autotecnico-online.com).
Important Tips And Suggestions
TIP 1: The most effective way to test the MAF sensor on your Nissan Sentra is to test it while the engine is at normal operating Temperature and while it's running. Now, since you'll be working around a running engine, you'll need to be alert and take all safety precautions.
TIP 2:Three of four wires that come out of the mass air flow sensor connect directly to the fuel injection computer, so you have to be very careful not to short these to 12 Volts, or you'll fry the computer.
TIP 3: You can use a digital or an analog multimeter. Both will work, although the digital one is the preferred one due to its accuracy and rapid Signal response.
How Does The MAF Sensor Work?
In a nutshell, this is how the mass air flow sensor works:
- When you turn the Key to the ON position and then start the engine, the MAF gets power thru' the wire labeled with the number 4. This power is in the form of 5 Volts.
- Ground is provided by the fuel injection computer thru' the circuit labeled with the number 3. The computer also provides a 5 Volt Reference Signal thru' the wire labeled with the number 2.
- As the air enters the engine, the MAF sensor measures the amount of air flow and sends this info the fuel injection computer.
- When you accelerate the engine, the throttle plate opens and the MAF sensor immediately measures the change in the amount of air entering and sends this info to the fuel injection computer. This is accomplished thru' the wire labeled with the number 1.
- When you let go of the accelerator pedal, the throttle closes and since the MAF is always sensing, it now sees the change in air flow and sends this new info to the computer.
- The fuel injection computer uses this info (that the MAF sensor provides) to control fuel injection, ignition advance and host of other things to keep your engine running smoothly.
TEST 1: Verifying The MAF Sensor Is Getting Power
The very first thing you'll do, is test to make sure the MAF sensor on your 1.8L Nissan Sentra is getting power.
You can accomplish this test by using either a multimeter or a 12 Volt automotive test light, altho' the testing instructions assume you're using a multimeter.
You can check for this voltage with the MAF connected to its connector or not, the important thing to remember, if you do this test with it disconnected is NOT to probe the front of the connector. Probing the front of the connector will damage the metal female terminals.
These are the steps:
- 1
Probe the wire that's labeled with the number 4 in the photo.
To avoid probing the front of the terminal/connector, my suggestion is to use an appropriate tool to pierce the wire and then connect the red multimeter test lead to it. - 2
Ground the black multimeter test lead. For the best result, connect it on the battery negative (-) terminal.
- 3
Now, turn the Key to the ON position but do not crank or start your Nissan Sentra.
- 4
With the multimeter in Volts DC mode, it should register about 11 to 12 Volts DC.
Let's find out what your test result means:
CASE 1: The multimeter registered 12 Volts: this result confirms the MAF sensor on your Nissan Sentra is being fed with power. The next step is to check the Ground circuit. Go to: TEST 2: Verifying The MAF sensor Is Getting Ground.
CASE 2: Multimeter DID NOT register 12 Volts: Recheck all of your test connections and repeat the test. If still no voltage, then this result exonerates the MAF sensor since without power, it's not gonna' work.
Finding the source/cause of this missing voltage will get your MAF sensor back to functioning.
Altho' it's beyond the scope of this article to test for this missing voltage, the most common cause for this condition is one of two things: An open-circuit problem in the wire between the sensor and the computer, or a bad computer. You have at least eliminated the MAF sensor itself as the cause of the problem.
