How To Test The MAF Sensor (1990-1992 2.3L Ford Ranger)

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

TEST 1 confirmed that the MAF sensor is getting 12 Volts. In this section, we'll verify that the MAF sensor receives chassis Ground.

The MAF sensor receives chassis Ground from the black with white stripe (BLK/WHT) wire of the MAF sensor connector.

The BLK/WHT wire connects to the terminal marked with the letter B in the photo above.

If Ground is supplied by the BLK/WHT wire, we'll proceed to TEST 3.

NOTE: You won't be able to test the front of the terminal. To check for Ground, 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).

This is what you need to do:

1. 1

   Disconnect the MAF sensor from its electrical connector.

2. 2

   Place your multimeter in Volts DC mode.

3. 3

   Connect the black multimeter test lead to the BLK/WHT wire of the MAF sensor connector.

4. 4

   Connect the red multimeter test lead probe the battery positive (+) terminal.

5. 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 take a look at what your test results mean:

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. This test result indicates the MAF sensor is not receiving chassis Ground.

Recheck all of your multimeter connections and retest. If your multimeter still does not register 10 to 12 Volts, then this exonerates the MAF sensor as bad since without this Ground it will not function.

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

Now we'll check the second Ground circuit of the MAF sensor. This Ground is provided internally by the fuel injection computer.

The MAF sensor gets Ground from the fuel injection computer from the tan with light blue stripe (TAN/LT BLU) wire of the MAF sensor connector.

The TAN/LT BLU wire connects to the terminal marked with the letter C in the photo above.

We'll do a simple multimeter voltage test to check for the presence of Ground in the TAN/LT BLU wire.

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.

NOTE: You won't be able to test the front of the terminal. To check for Ground, 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).

OK, these are the steps:

1. 1

   Disconnect the MAF sensor from its electrical connector.

2. 2

   Place your multimeter in Volts DC mode.

3. 3

   Connect the black multimeter test lead to the TAN/LT BLU wire of the MAF sensor connector.

4. 4

   Connect the red multimeter test lead probe the battery positive (+) terminal.

5. 5

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

6. 6

   You should see 10 to 12 Volts on the multimeter.

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

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, for this, 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.

Recheck all of your multimeter connections and retest. If your multimeter still does not register 10 to 12 Volts, then this exonerates the MAF sensor as bad since without this Ground it will not function.

TEST 4: Testing The MAF Signal

The previous tests have confirmed the following:

• The MAF sensor is receiving power (TEST 1).
• The MAF sensor is receiving chassis Ground (TEST 2).
• The MAF sensor is receiving Ground from the PCM (TEST 3).

In this final section, we'll check the performance of the MAF sensor with the engine running.

If the MAF sensor is working properly, its voltage signal should increase as the engine speed increases. As the engine speed decreases, the voltage signal should decrease.

Generally, when the MAF sensor fails, it generates a voltage signal that stays stuck in one value regardless of engine speed.

The wire we'll be testing for the MAF sensor signal voltage is the light blue with red stripe (LT BLU/RED) wire of the MAF sensor connector.

IMPORTANT: Start the engine and allow it to warm up to normal operating temperature before beginning the test procedure.

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).

Let's start:

1. 1

   Reconnect the MAF sensor to its electrical connector.

2. 2

   Place your multimeter in Volts DC mode.

3. 3

   Connect the red multimeter test lead to the LT BLU/RED wire using a suitable tool.

4. 4

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

5. 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. 6

   Open the throttle (manually) to increase engine speed.

7. 7

   The voltage value should increase as the engine speed increases.

8. 8

   Release the throttle to decrease engine speed.

9. 9

   The voltage value should decrease as the engine speed decreases.

10. 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 voltage value increased/decreased as you accelerated/decelerated the engine. This tells you that the MAF sensor is good and not the cause of the MAF issue or diagnostic trouble code.

CASE 2: The voltage value stayed stuck in value as you accelerated/decelerated the engine. Recheck all of your multimeter connections and retest.

If you still do not see the indicated voltage rising and falling smoothly, then you can conclude 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 when you accelerate/decelerate the engine (this test section).

More 2.3L Ford Ranger Diagnostic Tutorials

You can find a complete list of 2.3L Ford Ranger (Mazda B2300) tutorials in this index:

• Ford 2.3L Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

• How To Test The MAF Sensor (1995-1997 2.3L Ford Ranger).
• How To Test The Ignition Module And Crank Sensor (2.3L Ranger, Mustang, B2300).
• Testing The Blower Resistor (1995-1997 2.3L Ford Ranger) .
• How To Test For A Blown Head Gasket (1989-1997 2.3L Ford Ranger).