How To Test The MAF Sensor (1997, 1998 3.0L Mitsubishi Montero)

The mass air flow (MAF) sensor on your 3.0L equipped Mitsubishi Montero can be easily tested with just a multimeter to find out if it has 'kicked the bucket' (or not).

Testing it is also a time and money saver 'cause the MAF sensor is a pretty expensive part! In this tutorial, I'll show you how to diagnose it in a step-by-step way.

You can find this tutorial in Spanish here: Cómo Probar El Sensor MAF (1997, 1998 3.0L Mitsubishi Montero) (at: autotecnico-online.com).

Symptoms Of A Bad Mass Air Flow 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:

1. A MAF sensor diagnostic trouble code (DTC) stored in your vehicle computer's memory.
   • P0101 Volume Air Flow Circuit Range/Performance Problem.
   • P0102 Volume Air Flow Circuit Low Input.
   • P0103 Volume Air Flow Circuit High Input.
2. Lean and/or Rich diagnostic trouble code(s).
   • P0171, P0174
3. Fuel trim diagnostic trouble code(s).
4. No power when you accelerate the car or truck.
5. Black smoke coming from the tail-pipe.
6. Your Montero idles rough and/or stalls.

What Tools Do I Need?

Here's a basic list of tools you'll need to test the MAF sensor with the help of this tutorial:

• A digital multimeter that can read 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).
• A back probe or wire piercing probe. To see what a wire-piercing probe looks like, go here: Wire Piercing Probe.
• A scan tool or code reader to read trouble codes (you don't need an automotive scan tool to test the MAF sensor. Having said that... a scan tool is one of those MUST have tools to be able read trouble codes lighting up the CEL).

The most important tool you'll need is the digital multimeter that can read Hertz frequency.

Circuit Descriptions Of The MAF Sensor Connector

All of the tests I'm gonna' describe involve testing some sort of signal on the wires of the mass air flow (MAF) sensor connector and not on the MAF sensor itself.

IMPORTANT: The illustration above is the front view of the MAF sensor connector. The front view of the connector makes it easier to identify the correct circuit to test only. You should never probe the front of the connector's terminal with your multimeter's test lead or you'll damage the terminal.

Your Mitsubishi Montero's mass air flow (MAF) sensor has a total of 7 wires coming out of the connector. To find out if the MAF sensor is bad (or not) we don't need to test every single circuit, I've included the circuit descriptions of all 7 wires anyway for your viewing pleasure.

• Circuit labeled 1:
  • 5 Volt Reference Voltage
• Circuit labeled 2:
  • Barometric Pressure Sensor Circuit
• Circuit labeled 3:
  • MAF Signal Output.
• Circuit labeled 4:
  • Power (12 Volts) Circuit.
• Circuit labeled 5:
  1. Sensor Return (Ground) Circuit.
• Circuit labeled 6:
  • Intake Air Temp Sensor Circuit.
• Circuit labeled 7:
  • MAF Reset Signal Output Circuit.

I did not include the color of the wires because as long as you're able to identify them by the number in the photo, you'll be OK. Also, the color of the wires in the photos may not be the color of the wires of the MAF on your specific vehicle and again this is no cause for concern as long as you're testing the MAF sensor for the 1997-1998 3.0L Mitsubishi Montero.

TEST 1: Testing The Power Circuit For 12 Volts

To get the MAF sensor diagnostic under way, we'll start by checking and confirming that the MAF sensor is getting power.

This power is in the form of battery voltage (12 Volts) and comes from the Multiport Fuel Injection Relay in the engine compartment relay box.

These are the test steps:

1. 1

   Place the multimeter in Volts DC mode.

2. 2

   Connect the red multimeter test lead to the wire that connects to the connector terminal identified with the number 4 (see the illustration above) using an appropriate tool.

3. 3

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

4. 4

   Turn the key ON but don't crank or start the engine.

5. 5

   The multimeter should register between 10 to 12 Volts DC.

Let's take a look at what your test results mean:

CASE 1: The multimeter registered 10 to 12 Volts DC. This is the correct test result and confirms that the MAF sensor is getting juice (12 Volts).

The next step is to verify that it's also getting a good Ground, go to: TEST 2: Testing The Ground Circuit.

CASE 2: The multimeter DID NOT register 10 to 12 Volts DC. Your next step is to find out why this voltage is missing since without power, the MAF sensor won't work. Repairing the cause of the missing voltage will solve the MAF sensor issue/problem lighting up the check engine light on your Mitsubishi Montero.