The mass air flow meter or MAF sensor in your Mazda 626 is the primary way that your Mazda engine control unit (ECU) operates your engine. When there’s a problem with your MAF sensor or issues with your intake tract, it can cause your Mazda to run rough or idle roughly. There can be several things that can cause your Mazda 626 MAF sensor to fail, or having intermittent issues.
Many people think that the only way you can test a Mazda 626 MAF Sensor is to take it to a mechanic or using a OBDII scan tool. Actually the only thing you really need is a multimeter or voltmeter to determine whether your sensor is any good, or it needs replacing. Not sure how to use one or don’t know what a multimeter is? Check out our guide here.
Today I’ll be showing you how to test the MAF sensor in your 2.0 liter Mazda 626. Our test vehicle is a 2000 Mazda 2.0 liter 626, but this how to guide applies to the year ranges from 1997-2002.
What does the Mazda 626 MAF sensor do? When your engine is turned on, the incoming air charge is monitored and analyzed by your mass air flow sensor. There are many different kinds of metering systems, from karman to hot-wire but they all do the same thing.
By reading the amount of incoming air, the temperature of the air and more, the Mazda ECU can accurately deliver the right amount of fuel and control ignition events to safely operate your 2.0 liter engine.
When your Mazda 626 MAF sensor fails, there are several symptoms that you will see. One of the most common problems is a check engine light being lit on your dashboard.
Some of the most common Mazda check engine trouble codes are :
- P0101 – MAF Sensor Performance Problem
- P0102 – Low Input MAF Sensor Signal
- P0103 – High Input MAF Sensor Signal
There are other symptoms with your Mazda that can happen when your MAF begins to fail. Here are some of the most common Mazda symptoms that can occur.
- Rough Idle
- Mazda doesn’t start
- Black smoke from tailpipe
These issues occur when the Mazda ECU doesn’t know how much air is coming into the engine. You can also have these problems when your intake tract has leaks in it, or is sucking in air after the MAF unit. This represents non-metered air that’s entering into the engine, that can create a lean condition or dangerous engine air fuel ratios
The 4 pin Mazda MAF sensor is located in your intake system, directly to the right of your 2.0 liter Mazda engine. Unplugging this MAF is easy to do, and once you have your multimeter ready, you can begin testing your Mazda 626 MAF sensor to see if it’s failed or not.
The first set of wires we’ll be working on is your power and ground signals. You will begin at PIN D which should be a red wire with a green stripe in it. To test this unit, insert your car key and turn your Mazda ignition to the “ON” position. With your MAF sensor plugged in, you will be backpinning your probing the red wire with black stripe or a 12 volt signal.
Do this by connecting the black lead of your multimeter to the negative terminal of your battery, and then backprobing pin D with the red lead.
Once you have checked PIN D, move onto the low reference signal or ground wire. We’ll start with the chassis ground, which is the brown wire with RED stripe, or PIN C. You can check this ground by backpinning the second wire to check for ground.
The next wire you will be checking is PIN B which is a black wire with a red stripe. This is a ECM ground, and cannot be checked with the MAF connector unplugged. Make sure that your Mazda ECU is providing a MAF ground to this pin.
If you do not have power and ground at these three wires, there’s a huge issue with your wiring or a fuse. Make sure to check your vehicle grounds, and check the continuity between your Mazda MAF connector and your ECU connector.
The last wire we are testing in this how-to procedure is the MAF signal wire. This wire is red with a green stripe, and it’s PIN A. Because this is the signal wire, you will be able to determine whether or not the MAF sensor is working correctly by tapping into this wire. Like the ECU ground, you obviously cannot test this wire without the MAF connected.
If your MAF sensor is receiving power and ground, but your 626 is still running rough or having issues, there may be an intermittent issue with your MAF. To test this, you must measure or tap into PIN A to see what the values being sent to your Mazda ECU are.
*** Because this part of the Mazda 626 MAF sensor test will require you to start your engine, use extreme precaution. Make sure you are not wearing any loose clothing and stay clear of all power accessories, belts and fans.
Not sure or not comfortable? Skip this part and take it to a professional who can properly measure the output of your MAF sensor.
Reconnect the MAF sensor and make sure to reference our wiring diagram above in reverse, as the diagram is displayed from the face of the connector.
Start your engine and place the black lead of your multimeter to the negative battery. Turn the dial on your multimeter to volts DC and then probe PIN A, which is the signal wire that’s RED with a green stripe.
With the multimeter lead connected to this wire, your Mazda MAF sensor should be sending a voltage signal between 1.5 and 1.8 volts. If this reading shows good, you can now either manually depress your Mazda 626 throttle blade, or have a helper rev the engine. Make sure the transmission is in neutral or the PARK position before doing this.
As you rev the engine, the voltage from your mass air flow meter should rise, reaching 3 volts around 4500 RPM. Slowly rev the engine and allow it to decelerate, and you should see the voltage sweep evenly on your multimeter.
There shouldn’t be any gaps or spikes in the voltage as you rev the 2.0 liter Mazda engine. If you do see any issues with the voltage signal, go ahead and replace the MAF to restore your Mazda 626 operation.
The part number for your 2.0 liter Mazda 626 MAF sensor is 49-00527 AN for a new model, or you can source a refurbished one.