In this test tutorial, I'll show you how to test the mass air flow sensor to see if its BAD (and lighting up the check engine light) or not. This MAF test is done in 3 easy steps.
All you'll need, to test the MAF sensor (with this tutorial) is a multimeter that can read Hertz frequency (if you don't have one, I've made a recommendation on where you can buy a reasonably priced one below).
In case this isn't the MAF sensor article you're needing, there are several more I've written and you can find some of them here:
- How To Test The GM mass air flow sensor (Early Type): Buick, Chevy, Olds, Pontiac 3.1L, 3.4L, 4.3L, 5.0L, 5.7L V6 Engines (1996-2005)
- How To Test The GM MAF Sensor: Buick, Chevy, Olds, Pontiac 3.8L V6 Engines (1996-2005)
- How To Test The GM Mass Air Flow (MAF) Sensor: 4.8L, 5.3L, 6.0L, and 8.1L V8 Engines (1999-2010)
- How To Test The MAF Sensor on 3.1L, 3.3L, and 3.8L Buick, Oldsmobile, Pontiac (1988-1996)
You can find this tutorial in Spanish here: Cómo Probar El Sensor MAF (2005-2007 3.5L GM) (at: autotecnico-online.com).
Symptoms Of A BAD GM MAF Sensor
The most obvious one is that the CHECK ENGINE light (CEL) will be on on your instrument cluster and driving you nuts. Here are a couple of others:
- A MAF sensor diagnostic trouble code (DTC) stored in your vehicle computer's memory.
- P0100: Mass Air Flow (MAF) Sensor Circuit Malfunction.
- P0101: Mass Air Flow (MAF) Sensor Circuit Range/Performance Problem.
- P0102: Mass Air Flow (MAF) Sensor Circuit Low Input.
- P0103: Mass Air Flow (MAF) Sensor Circuit High Input.
- Lean and/or Rich Diagnostic Trouble code(s).
- P0171: System Too Lean (Bank 1).
- P0172: System Too Rich (Bank 1).
- P0174: System Too Lean (Bank 2).
- P0175: System Too Rich (Bank 2).
- Fuel Trim diagnostic trouble code(s).
- No Power when you accelerate the car or truck.
- Black smoke coming from the tail-pipe.
- Your car or truck or SUV may idle rough and stall.
What Tools Do I Need?
A Scan Tool is one of those MUST have tools to be able check and diagnose today's modern cars and trucks, but for the tests in this article you don't need one.
This are the tools you need or may need:
- A digital one that can read Hertz frequency is a must have tool to test the MAF sensor on your vehicle.
- If you need to buy one or are looking to upgrade, check out my recommendations here: Buying A Digital Multimeter For Automotive Diagnostic Testing.
- Wire Piercing Probe
- Although not an absolute must, this tool is a time saver of the first order. To see what this tool looks like, click here: Wire Piercing Probe.
Circuit Descriptions Of The MAF Sensor Connector
The MAF sensor covered by this tutorial has 5 wires coming out of the connector. Each wire (circuit) has a specific job to do and below you'll find the description. Each of the 3 Tests, that make up this article, will use these circuit descriptions:
- Circuit labeled A:
- Yellow wire. MAF Sensor Signal
- Circuit labeled B:
- Pink w/ Black stripe wire. Ignition voltage (10 to 12 Volts DC).
- Circuit labeled C:
- Black w/ White stripe wire. Ground Circuit.
- Circuit labeled D:
- Tan wire. Air Temperature Sensor Circuit
- Circuit labeled E:
- Tan w/ Black stripe wire. Air Temperature Sensor Circuit (low reference = ground).
Basic Working Theory Of The GM MAF Sensor
The fuel injection computer needs to know the amount of air the engine is breathing to inject the correct amount of fuel (among several things) and keep your GM vehicle idling, running smooth, accelerating, polluting less, etc. For this, the PCM relies on the mass air flow sensor, among several of the sensors that monitor the engine and transmission.
The MAF sensor's job is to measure the amount of air the engine is breathing at any given RPM. It then converts this measurement into a Hertz frequency reading (as measured by a digital multimeter that can read Hz Frequency) and shoots it to the PCM. Here's what it looks like on a digital multimeter:
- At an idle of about 680 RPM's, the MAF sensor outputs about 3.2 K Hertz.
- Let me emphasize the words ‘outputs about’ because every vehicle will output a slightly different value depending on several conditions like: engine temperature, ambient air temperature, etc.
- At about at 1500 RPM;s the MAF signal output is about 4.2 K Hz.
- At 2500 RPM's it hovers around 5.2 K Hz.
As you can see, the more air the engine breathes (or the higher the RPM's) the higher the MAF output signal becomes, and of course the less air the engine breathes, the lower the reading on your digital multimeter.
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. OK, crash course is over, let's start testing.