Testing the MAF Signal of the Mass Airflow Sensor!


Now that the basics have been checked, we'll check the MAF signal coming out of the sensor and going to the ECM with a multimeter. Here's how to do it...
Start the engine and let it reach it's normal operating temperature. You'll be using the Voltage reading you will obtain at idle as a base to diagnose the MAF Sensor.
The MAF Sensor must be connected to its connector to perform this test.
With the key in the OFF position.
With a suitable tool connected to the RED multimeter lead, probe the B circuit of the MAF Sensor connector shown in the photo.
Put the multimeter in VOLTS DC mode.
Connect the BLACK lead to the Battery (-) Negative Terminal.
Start the already warmed up engine.
Note the Volts reading on your multimeter at idle. 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 reading.
Accelerate the engine as you watch the multimeter's Voltage readings.
The Voltage numbers should correspond to the amount of acceleration.
Repeat this as often as you need to verify that the Voltage numbers on the multimeter rise smoothly every single time.
If the MAF Sensor is good, these readings will not spike up and down crazily but will correspond to the amount of air the engine is breathing at the different RPMs you're accelerating the engine to.
Did the signal rise smoothly with each increase in engine acceleration and stay steady at idle?
YES- The MAF Sensor is functioning correctly.
NO- The MAF Sensor is defective. Replace MAF Sensor