This is one of the easiest MAF sensors on the planet to test! It just takes three steps to find out if the MAF sensor is bad or not. No automotive scan tool is needed for this test! As is the custom on this site, I'll take you thru' the whole process step by step.
This section of the tutorial deals with some very basic working theory of how the 2.6L Isuzu Pick Up (Rodeo, Amigo) MAF works, some do's and don'ts, common symptoms, and some other good stuff.
Puedes encontrar este tutorial en Español aquí: Cómo Probar El Sensor MAF 2.6L Amigo, Pick Up, Rodeo (1993-1996) (en: autotecnico-online.com).
Well, let's get started.
The Most Common Symptoms Of A Bad MAF Sensor
The most common symptoms of a defective MAF sensor are:
- A MAF sensor code.
- Lean and/or Rich code(s).
- Fuel trim code(s).
- A tremendous lack of power upon acceleration.
- Black smoke coming from the tail-pipe.
- Vehicle may idle rough and stall.
The Most Common Problems With An Isuzu MAF Sensor
The two most commons problems I have diagnosed and repaired on these older Isuzu SUV have been: 1) Dirty (contaminated) mass air flow sensor, 2) Air leaks between the MAF sensor and the throttle body.
Let's tackle the dirty MAF sensor first: This MAF sensor is a hot-wire type that easily becomes contaminated with dirt and stuff from the air filter not performing its job. Cleaning this type of sensor is super easy since the sensor's ‘hot-wires’ are clearly visible to the eye (with the sensor removed of course!).
Since this contamination will cause the sensor to produce a lower reading to the ECM (Engine Control Module = Fuel Injection Computer). The most common symptom of this contamination is a hesitation or a time-lag in engine responce that is felt after the accelerator pedal is depressed.
If cleaning the MAF sensor, use an electronics spray cleaner to do it with. This in itself may solve your problem. Don't use carburetor or brake clean spray or gasoline. These solvents can damage the sensor. Also, don't attempt to physically clean the sensor with anything. Your local auto part store will have MAF sensor cleaning spray or something similar.
Air leaks between the MAF sensor and the throttle body. This is the second most common problem I have seen on these Isuzu SUV's. Either the air duct that connects these two components is loose and allowing air to enter the engine after the air has been metered by the sensor or the air duct is torn.
Any of these two conditions will cause the fuel injection computer to get an incorrect MAF signal and your Isuzu will suffer for it. Not only that, these two conditions will cause your tests to produce a result that may make you think the MAF sensor is bad, thus replacing it when it's actually good.
Therefore, I recommend that you check for these two conditions first before jumping into the tests.
Where Do I Start?
OK, you're gonna' start by checking the basics. These are 12 Volts and battery Ground to the MAF sensor. After that, we'll test the actual performance of the MAF sensor as the engine is running. Use a digital multimeter for all tests where a multimeter is called for.
The MAF sensor produces an analog DC voltage MAF signal. At idle with the engine at its normal operating temperature, the Isuzu MAF sensor produces a MAF signal of 1.0 Volts to 1.7 Volts. The MAF sensor's operating voltage range is from .0 to 5 Volts.
The important thing to know and understand is that the MAF signal's voltage is directly related to amount of air the engine is breathing. As you already know, the higher the engine RPM's, the more air the engine breathes than at lower RPM's. For example: the amount of air entering the engine at 3,000 RPM's RPM's is higher than at 900 RPM's. And so the DC Voltage value on the multimeter will be greater at those 3000 RPM's than at 900 RPM's
Now, when testing this voltage signal, the important thing to know is not an actual DC Volts number at a specific RPM, but to look for crazy and extreme fluctuations in the voltage signal that do not correspond to the actual air intake (RPM's) of the engine or NO SIGNAL AT ALL. For example: If at Idle the voltage reading starts to spike up and down without you accelerating the engine or no signal being registered at all on your multimeter.
In the TEST 3 section of this article, I'll show how you'll use a base voltage reading at idle from the MAF sensor that will help you to confirm that the MAF sensor is bad or not.
TEST INFO: 2.6L Isuzu MAF Sensor Circuit Descriptions
The safest way to test these circuits, and the method I always use, is using a wire piercing probe. (Wire Piercing Probe). Using this probe, I don't have to disconnect the MAF sensor's connector to probe the front of the female terminal and possibly risk damaging it.
Independent of the method you use, be careful not to damage the wire or the female terminal. Take all safety precautions.
IMPORTANT: All of the tests are ON CAR TESTS, do not remove or disconnect the mass air flow sensor from the vehicle or from its plumbing.
As you've already noticed, the photo (above) has the MAF connector numbered 1 thru' 3. I'll be using these numbers for the circuit descriptions. Here's the description of each circuit below.
- Letter C- MAF signal.
- Letter B- Ground provided by the ECM internally.
- Letter A- 12 Volt battery power.
We're ready to get started...