Testing to see if the MAF Sensor on your 3.5L GM equipped car or pickup or SUV is BAD or not can easily be done with a Multimeter.
In this article I'll show you how to do it in a step-by-step fashion... that will either condemn the Mass Airflow (MAF) Sensor as BAD or exonerate it.
This MAF Sensor is not cheap... so being able to say that it's truly BAD or not will save you some money.
To help you navigate this article, here are its main points:
When the MAF Sensor goes BAD, you'll get the Check Engine Light to shine nice and bright on your Instrument Cluster.
You'll also see one or several of the following symptoms of a BAD MAF Sensor:
It's rare for the Mass Air Flow (MAF) Sensor to go BAD and not leave a Diagnostic Trouble Code... but sometimes you'll get the MAF Trouble Code and the MAF is good. So, it's always a good idea to test it.
Here's a basic list of tools you'll need:
A Scan Tool comes in handy... but you won't need it to use the testing info in this article.
The MAF Sensor is tasked with measuring the amount of air entering the engine at any given RPM. The PCM (Powertrain Control Module = Fuel Injection Computer) then uses this measurement of air flow to inject the correct amount of fuel.
To get into more specifics: The MAF Sensor informs the amount of air flow by converting the measurement of air into a Hertz Frequency signal that increases with more air flow (as you accelerate the Engine) or decreases as the Engine breathes less air.
This Hertz Frequency signal is sent directly to the PCM. Here’s what it looks like on a Digital Multimeter (that can read Hertz):
The important thing to know, is that the more air the engine breathes (or the higher the RPM’s) the higher the MAF Hertz signal becomes, and of course the less air the engine breathes, the lower the Hertz signal (that your Digital Multimeter will record).
Now, in testing the MAF Sensor, you won’t be looking for a specific Hertz (Hz) number at a specific RPM... but for crazy fluctuations in the Signal that don’t correspond to the amount of air entering the engine or NO SIGNAL AT ALL.
These are the circuit descriptions of the Mass Air Flow (MAF) Sensor
|MAF Sensor Connector Pin Out|
|A||Yellow||MAF Sensor Signal Output|
|B||Black w/ White stripe||Chassis Ground|
|C||Pink||12 V. Ignition Fused Feed|
|D||Tan||Intake Air Temp (IAT) Sensor|
|E||Black||Intake Air Temp (IAT) Sensor|
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