2.6L Isuzu MAF Sensor Test Amigo, Pick Up, Rodeo (1993-96)

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.

You can find this tutorial in Spanish here: Cómo Probar El Sensor MAF 2.6L Amigo, Pick Up, Rodeo (1993-1996) (at: autotecnico-online.com).

The Most Common Symptoms Of A Bad MAF Sensor

The most common symptoms of a defective MAF sensor are:

1. A MAF sensor code.
2. Lean and/or Rich code(s).
3. Fuel trim code(s).
4. A tremendous lack of power upon acceleration.
5. Black smoke coming from the tail-pipe.
6. 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 RPMs, the more air the engine breathes than at lower RPMs. For example: the amount of air entering the engine at 3,000 RPMs RPMs is higher than at 900 RPMs. And so the DC Voltage value on the multimeter will be greater at those 3000 RPMs than at 900 RPMs

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 (RPMs) 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.

1. Letter C- MAF signal.
2. Letter B- Ground provided by the ECM internally.
3. Letter A- 12 Volt battery power.

We're ready to get started...

TEST 1: Testing The MAF Signal With A Multimeter

To get started, we'll check the MAF signal coming out of the sensor and going to the ECM.

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 voltage to diagnose the MAF sensor.

If the MAF sensor is defective, it'll stay stuck producing a fixed voltage value as you rev up/down the engine.

If the MAF sensor is functioning correctly, it's MAF voltage signal will increase/decrease as you rev up/down the engine.

NOTE: The MAF sensor, on your 2.6L Pick Up (Rodeo, Amigo), must be connected to its connector to perform this test.

This is what you need to do:

1. 1

   Connect the red multimeter test lead to the wire labeled with the letter C in the photo above.

2. 2

   Put the multimeter in Volts DC mode.

3. 3

   Connect the black lead to the battery negative (-) terminal.

4. 4

   Start the already warmed up engine.

5. 5

   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.

6. 6

   Accelerate the engine as you watch the multimeter's voltage readings.
   
   The voltage value should increase as you rev up the engine.
   
   The voltage value should decrease when you let the engine return to idle.

Did the signal rise smoothly with each increase in engine acceleration and stay steady at idle?

CASE 1: The MAF signal increased/decreased as you revved up/down the engine. This result confirms the MAF sensor is OK.

To explain this a bit further: What you're looking for is for the multimeter's voltage reading to increase as you rev up the engine and then see the voltage decrease as the engine slows down. There's no specific voltage value at a specific engine RPM that you're looking for since just seeing the MAF voltage signal increase/decrease as you rev up/rev down the engine is enough to conclude the MAF sensor is OK.

CASE 2: The MAF signal DID NOT increase/decrease as you revved up/down the engine. This result usually means the MAF sensor has failed.

To be sure the MAF sensor is bad, we need to make sure it's getting power and Ground. For the first of these two tests, go to: TEST 2: Testing The Power Circuit.