How To Test The MAF Sensor (1991-1994 3.0L V6 Ford Ranger)

By: Abraham Torres-Arredondo
Created: 23 November 2022
Updated: 16 March 2024
Articl Id: 1433

Page 2 of 2

TEST 2: Making Sure The MAF Sensor Is Getting Chassis Ground

MAF Sensor Circuit Descriptions. How To Test The MAF Sensor (1991, 1992, 1993, 1994 3.0L V6 Ford Ranger And Mazda B3000)

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For our second test, we'll check that the black with white stripe (BLK/WHT) wire of the four-wire connector supplies chassis Ground to the MAF sensor.

In the illustrations of the MAF sensor connector above, the BLK/WHT wire connects to the terminal labeled with the letter B.

A simple voltage test is enough to confirm that the BLK/WHT wire provides chassis Ground to the MAF sensor.

Let's begin:

1
Disconnect the MAF sensor from its electrical connector.
2
Place your multimeter in Volts DC mode.
3
Connect the black multimeter test lead to the BLK/WHT wire of the MAF sensor connector.

The BLK wire connects to the terminal labeled with the letter B of the MAF sensor 4-wire connector.
4
Connect the red multimeter test lead probe the battery positive (+) terminal.
5
You should see 10 to 12 Volts on the multimeter.

NOTE: No need to turn the key to the ON position since this is a chassis Ground and is available at all times.

Let's interpret your test result:

CASE 1: Your multimeter registered 10 to 12 Volts. This is the correct result and confirms chassis Ground is available to the MAF sensor.

The next step is to make sure the MAF sensor is getting Ground from the fuel injection computer, for this, go to: TEST 3: Making Sure The MAF Sensor Is Getting Ground (PCM).

CASE 2: Your multimeter DID NOT register 10 to 12 Volts. Without chassis Ground the MAF sensor will not function.

This test result tells you that the MAF sensor itself is not faulty. Your next step is to find out why chassis Ground is missing and restore it to the BLK/WHT wire.

TEST 3: Making Sure The MAF Sensor Is Getting Ground (PCM)

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The previous two tests confirmed the following:

The MAF sensor is getting power (TEST 1).
The MAF sensor is getting chassis Ground (TEST 2).

The focus of this third test section is to check that the tan with light blue stripe (TAN/LT BLU) wire is providing Ground to the sensor.

This second Ground is provided by the fuel injection computer.

CAUTION: Be careful when testing this circuit! Do not connect this wire directly to 12 Volts. Otherwise you'll damage the fuel injection computer. The multimeter test suggested below is a safe way to test for the presence of Ground in the wire.

Let's get started:

1
Disconnect the MAF sensor from its electrical connector.
2
Place your multimeter in Volts DC mode.
3
Connect the black multimeter test lead to the TAN/LT BLU wire of the MAF sensor connector.
4
Connect the red multimeter test lead probe the battery positive (+) terminal.
5
Turn the key to the ON position but don't crank or start the engine.
6
You should see 10 to 12 Volts on the multimeter.

Let's examine what your test result means:

CASE 1: Your multimeter registered 10 to 12 Volts. This is the correct result and confirms the fuel injection computer is providing Ground.

The next step is to check the MAF sensor signal with the engine running. Go to: TEST 4: Testing The MAF Signal.

CASE 2: Your multimeter DID NOT register 10 to 12 Volts. This test result indicates the MAF sensor is not receiving Ground from the fuel injection computer.

This test result also tells you that the MAF sensor itself is not faulty. Your next step is to find out why Ground is missing and restore it to the TAN/LT BLU wire.

TEST 4: Testing The MAF Signal

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The focus of this final test section is to check the performance of the MAF sensor signal.

Specifically, we want to see if the signal voltage increases/decreases with an increase/decrease in engine speed.

If the MAF sensor is bad, its signal voltage generally remains stuck at one voltage value, regardless of engine speed.

To be a bit more specific:

The MAF signal voltage increases when engine speed increases.
The MAF signal voltage decreases when engine speed decreases.

NOTE: It's important that the engine is at normal operating temperature. If the engine is cold, start it and let it reach normal operating temperature.

IMPORTANT: The MAF sensor must be connected to its connector to perform this test. You'll need to use a back probe on the connector or a wire piercing probe on the wire. You can see an example of this tool here: Wire Piercing Probe Review (Power Probe PWPPPPP01).

These are the test steps:

1
Reconnect the MAF sensor to its electrical connector.
2
Place your multimeter in Volts DC mode.
3
Connect the red multimeter test lead to the LT BLU/RED wire using a suitable tool.
4
Connect the black multimeter test lead to the battery (-) negative terminal.
5
Crank and start the engine and let her idle.

Once the idle stabilizes, take a look at the voltage number or numbers your multimeter is throwing at you. This voltage may fluctuate a little or a lot, and this is OK. Whatever they're doing, this is your base MAF signal voltage.
6
Open the throttle (manually) to increase engine speed.
7
The voltage value should increase as the engine speed increases.
8
Release the throttle to decrease engine speed.
9
The voltage value should decrease as the engine speed decreases.
10
Repeat steps 6 through 9 several times to make sure of your test result.

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

CASE 1: The signal voltage reading increased/decreased as you increased/decreased engine speed. This tells you that the MAF sensor is good.

CASE 2: The signal voltage reading DID NOT increase/decrease as engine speed increased/decreased. This test result tells you that the mass air flow (MAF) sensor is bad if you have:

Confirmed the MAF sensor is receiving power (TEST 1).
Confirmed the MAF sensor is receiving chassis Ground (TEST 2).
Confirmed the MAF sensor is receiving Ground from the PCM (TEST 3).
Confirmed the MAF voltage signal does not increase/decrease as engine speed increases/decreases (this test section).