In this article, I'll show you how to test the mass air flow (MAF) sensor on your GM 3.8L (3800) vehicle without a scan tool.
Now, in case you wondering if this test applies to your specific vehicle, this article covers the MAF sensor on 1996 thru' 2005 3.8L V6 Buick, Chevrolet, Oldsmobile, Pontiac 3.8L V6 equipped cars. For more specific application info, take a look at the box titled Applies To: on the right column.
If you need to just clean the MAF sensor, you can find this article here: Cleaning The MAF Sensor (at: troubleshootmyvehicle.com). There are also several other MAF sensor test article I've written you might be interested in looking at:
- How To Test The MAF Sensor on 3.1L, 3.3L, and 3.8L Buick, Oldsmobile, Pontiac (1988-1996)
- 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 Mass Air Flow (MAF) Sensor: 4.8L, 5.3L, 6.0L, and 8.1L V8 Engines (1999-2010)
- How To Test The GM Mass Air Flow Sensor: GMC Savana Van and Chevy Express Van 4.3L, 5.3L, 6.0L Engines (2003-2008)
You can find this tutorial in Spanish here: Cómo Probar El Sensor MAF GM 3.8L (1996-2005) (en: autotecnico-online.com).
Common Symptoms Of A Bad GM MAF Sensor
This list covers the majority of symptoms I've seen on these types of GM mass air flow sensors:
- MAF codes that light up the check engine light (CEL) on your instrument cluster.
- P0101 Mass Air Flow System Performance.
- P0102 Mass Air Flow Low Frequency.
- P0103 Mass Air Flow High Frequency.
- MAF sensor malfunction that DOES NOT light up the check engine light (CEL).
- Lean and/or Rich code(s).
- Fuel Trim code(s).
- A tremendous lack of power upon acceleration.
- Black smoke coming from the tail-pipe.
- Bad gas mileage.
- Vehicle may idle rough and stall.
What Tools Do I Need?
As I mentioned at the beginning, you don't need a scan tool to follow the tests in this article, but you do need a multimeter.
This multimeter has to be a digital multimeter that can read high Hertz (Hz) Frequency (don't have a digital multimeter that can read Hertz frequency? Click here to see my recommendations: Buying A Digital Multimeter For Automotive Diagnostic Testing).
One other tool, that I recommend, is for you to use a wire-piercing probe to to test the signal of each wire (to see what this tool looks like, click here: Wire-Piercing Probe.
Circuit Descriptions Of The GM MAF Sensor Connector
As you're already aware, the MAF sensor on your vehicle is a 3 wire sensor.
Whether your driving a Buick, Chevy, Olds, or Pontiac vehicle (with a 3.8L V6) the circuits descriptions of the wires coming out of the Mass Air Flow (MAF) sensor are the same.
You'll notice that the photo above, I have the MAF connectors lettered A thru' C (if you look closely at the MAF sensor itself, you'll see these letters on it too). I'll be using these letters for the circuit descriptions. Here's the description of each circuit below:
- Letter A:
- MAF Signal.
- Letter B:
- Letter C:
- Power (12 Volts).
The one circuit that has to be tested with the connector connected to the MAF sensor is circuit A. This is the one that delivers the MAF signal that the MAF sensor creates to the PCM. The best way to get to this signal, inside the wire, is to use a wire piercing probe.
How Does The MAF Sensor Work?
The MAF sensor's job is to measure the amount of air that the engine is breathing. This measurement is accomplished by the sensor's two Hot Wires that are exposed to the incoming air.
The electronics inside the MAF sensor then convert this measurement of the airflow (as sensed by the two Hot Wires) into a high frequency digital signal. This signal can be measured with a digital multimeter that can read Hertz frequency or with an oscilloscope.
So, keeping this in mind, it's a given that the engine will breathe in more air at, let's say, 2,500 RPMs than when it's sitting at an idle of 900 RPMs and of course the Hertz reading will be higher at 2,500 RPMs than at 900 RPMs.
When testing this Hz frequency signal, the important thing to know is not an actual Hz frequency number at a specific RPM, but to look for crazy and extreme fluctuations in the Hz frequency signal that do not correspond to the actual air intake (RPMs) of the engine or NO SIGNAL AT ALL. In the TEST 3 section of this article, I'll show how you'll use a base Hz reading at idle from the MAF sensor that will help you to confirm that the MAF sensor is bad or not.
The MAF sensor test consists of verifying that the MAF sensor is receiving 12 Volts, Ground, and that it is indeed producing a correct MAF signal. This is an on-car test. Testing for these three signals is easy and I'll take you step by step thru' the whole test.