TEST 2: Verifying The MAF Sensor Is Getting Power
If in TEST 1 your Mazda's MAF sensor did not create an increasing/decreasing voltage signal as you revved the engine... the next step is to make sure that it's getting power.
The wire that delivers power, which is in the form of 12 Volts DC, to the MAF sensor is the red with black stripe (RED/BLK) wire of the engine wiring harness MAF sensor connector.
To check for this voltage, we'll do a simple multimeter voltage test. These are the steps:
NOTE: The connector in the image above is the actual MAF sensor connector for the 1996-1997 2.0L 626 and 1996-1997 2.0L MX6.
With your multimeter still in Volts DC mode from the previous test and the key on (but engine off).
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 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.
Now ground the multimeter's BLACK test lead on the battery's negative post.
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 (2.0L Mazda MX6).
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.
In this test section we'll make sure that the black with yellow stripe (BLK/YEL) wire of the MAF sensor electrical connector is feeding the MAF sensor with chassis ground.
Now, in case you're wondering what the heck is a ‘chassis’ ground... it's a ground wire that connects directly to the vehicle's chassis (body) or to a metal surface on the engine.
We can confirm this chassis ground with another simple multimeter voltage test.
These are the steps:
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.
Probe the BLK/YEL wire with the black multimeter test lead.
CAUTION: Do not probe the front of the connector or you risk damaging the female metal terminal of the connector.
Now connect the multimeter's RED test lead on the battery's positive (+) post.
If the BLK/YEL 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/YEL 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/YEL 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.