How To Test The MAF Sensor (1998-2002 2.0L Mazda 626)

TEST 2: Verifying The MAF Sensor Is Getting Power

If you've reached this point you've confirmed two very important things:

• That a mass airflow sensor trouble code (P0101, P0102, or P0103) is lighting up the check engine light on your instrument cluster.
• You have verified that in TEST 1 your mass airflow sensor's output signal did not increase or decrease as you revved up or revved down the engine.

So in this test we're going to make sure that the mass airflow sensor is getting power. This power is in the form of 12 Volts DC, and are provided by the red with black stripe (RED/BLK) wire, of the mass airflow sensor connector. To check for this voltage, we are going to do a simple multimeter test.

OK, these are the steps:

NOTE: The connector in the image above is the actual MAF sensor connector for the 1998-2002 2.0L 626.

1. 1

   With your multimeter still in Volts DC mode from the previous test and the key on (but engine off).

2. 2

   Disconnect the MAF sensor from its connector and probe the RED/BLK) wire of the MAF sensor connector. This is the wire that connects to the MAF sensor connector's female terminal A in the illustration above.
   
   CAUTION: Don't probe the front of the connector to avoid damaging the female metal terminal.

3. 3

   Now Ground the black multimeter test lead on the battery's negative post.

4. 4

   If the RED/BLK wire has power, your multimeter will register 10 to 12 Volts DC.

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

CASE 1: The RED/BLK wire, of the MAF sensor connector, has 10 to 12 Volts DC: This is the correct test result.

Now that you have confirmed that the MAF sensor is getting power, the next step is to check that it's getting Ground. Go to: TEST 3: Verifying The MAF Is Getting Ground.

CASE 2: The RED/BLK wire, of the MAF sensor connector, DOES NOT have 10 to 12 Volts DC: This results lets you know that the MAF sensor is not bad, since without these 12 Volts DC, the MAF sensor can not function.

Although it's beyond the scope of this article to troubleshoot the cause of these missing 12 Volts, you have now eliminated the MAF sensor as bad. Resolving the issue that is keeping these 12 Volts from being supplied will solve the MAF sensor issue on your 2.0L Mazda 626.

TEST 3: Verifying The MAF Sensor Is Getting Ground 1

Up to this point, your tests have confirmed that your Mazda 626's MAF sensor:

• Is lighting up the check engine light (CEL) with a MAF sensor trouble code: P0101, P0102, or P0103.
• Confirmed that the MAF sensor's voltage signal is stuck in one voltage value no matter how much you accelerate the engine (TEST 1).
• Checked the MAF sensor is getting power on the RED/BLK wire.

The mass air flow (MAF) sensor on your Mazda 626 is fed two different Grounds. The Ground that we're going to test in this section is the Ground that connects directly to chassis Ground. In other words this Ground wire connects to the battery negative cable via a connection on the engine.

We can confirm this chassis Ground with another simple multimeter voltage test.

These are the test steps:

1. 1

   Set your multimeter to Volts DC mode. Place the ignition key in its OFF position.
   
   NOTE: This Ground is a chassis Ground, so Ground is always available in this circuit.

2. 2

   Probe the BLK/RED wire with the black multimeter test lead.
   
   The black with red stripe (BLK/RED) wire is the one that connects to the MAF sensor connector's terminal B in the illustration above.
   
   CAUTION: Do not probe the front of the connector or you risk damaging the female metal terminal of the connector.

3. 3

   Now connect the red multimeter test lead on the battery's positive (+) post.

4. 4

   If the BLK/RED wire has Ground, then your multimeter will register 10 to 12 Volts DC.

OK, let's take a look at what your results mean:

CASE 1: The multimeter confirms that the BLK/RED wire is feeding Ground to the MAF sensor. This is the correct test result.

The next step is to check that your Mazda's fuel injection computer is feeding circuit C, of the MAF sensor, with Ground. For this test go to: TEST 4: Verifying The MAF Sensor Is Getting Ground 2

CASE 2: The multimeter confirms that the BLK/RED wire IS NOT feeding Ground to the MAF sensor. Double check your multimeter connections and repeat the test.

If your multimeter results still does not indicate 12 Volts, then the mass air flow (MAF) sensor is not fried and not the cause of the MAF sensor diagnostic trouble code (DTC) issue.

Here's why: Without a good path to chassis Ground, the MAF sensor will not work. With this test result, you have eliminated the MAF sensor itself as bad.