How To Test The MAF Sensor (2001-2007 Ford 3.0L V6 Ford Escape, Mercury Mariner)

The mass airflow (MAF) sensor on the 2001-2006 3.0L V6 Ford Escape (Mazda Tribute) is a hot wire type. And because of its location, it's a piece of cake to test since it's so accessible.

In this tutorial, I'm going to show you the four tests you can do to find out if it's good or if it's toast.

These four tests include checking its output voltage signal (MAF), making sure it's getting power (VPWR), and Ground (both PWR GND and MAF RTN).

And I almost forgot to mention that all four tests are done with a multimeter. No scan tool required and no other expensive diagnostic equipment.

APPLIES TO: This tutorial applies to the following vehicles:

• 3.0L V6 Ford Escape: 2001, 2002, 2003, 2004, 2005, 2006, 2007.
• 3.0L Mercury Mariner: 2005, 2006, 2007.
• 3.0L V6 Mazda Tribute: 2001, 2002, 2003, 2004, 2005, 2006.

Symptoms Of A Bad MAF Sensor

The only way your Ford Escape's Powertrain Control Module (PCM) can calculate the correct amount of fuel to deliver into the cylinders is by knowing how much air is entering the engine.

And you've guessed it —the engine management component tasked with this job is the mass airflow (MAF) sensor.

When it fails, the PCM can't fine-tune fuel delivery, and your Escape's V6 engine is going to be in a world of hurt. You'll see one or more of the following engine performance issues:

• Check Engine Light: The CEL will be lit on the dash, and the computer will usually store one of these codes:
  • P0102: MAF Sensor Signal Low.
  • P0103: MAF Sensor Signal High.
• Lack of power: Your Ford Escape's V6 engine may feel weak or hesitate when you hit the gas, especially under load or at higher speeds.
• Rough idle/stalling: The engine can idle unevenly or shut off on its own.
• Bad gas mileage: A bad MAF affects the PCM's ability to control the air-fuel mixture, making the engine run rich or lean, which kills gas mileage.
• Black exhaust smoke: If the PCM is adding too much fuel because of a bad MAF sensor signal, you may see black smoke coming out of the tailpipe.
• Hard starting: Sometimes the engine will crank but struggle to start.
• Hesitation or surging: You might feel the engine stumble or surge while accelerating or cruising.

MAF Sensor Circuit Descriptions

By now, I'm sure you've taken a look at the MAF sensor's connector and noticed that there are six wires coming out of it.

In the table below, you'll find a brief description of what each one does, which will help us in the MAF sensor tests to follow.

Pin	Wire	Description
1	Orange (ORG) –2001-2004 Only	IAT –Intake Air Temp Sensor Signal
	Gray with red stripe (GRY/RED) –2005-2007 Only
2	White with red stripe (WHT/RED)	VPWR –12 Volts Input in RUN or START
3	black (BLK)	PWR GND –Chassis Ground Input
4	Tan with light blue stripe (TAN/LT BLU)	MAF RTN –MAF sensor Ground (provided by PCM)
5	Light blue with red stripe (LT BLU/RED)	MAF –MAF signal
6	Gray (GRY)	SIG RTN –IAT sensor Ground

Where To Buy The MAF Sensor And Save

The following MAF sensors are from two brands (Walker and Delphi) I've used for many years and that I don't hesitate to recommend:

TEST 1: Testing The MAF Signal

The cool thing about the MAF sensor is that it reacts to the amount of air entering the engine in a very predictable way. In a nutshell:

• When airflow is low (like when engine RPM is low), the MAF sensor produces a low-voltage output signal.
• When airflow is high (like when engine RPM is up), the MAF sensor produces a voltage signal that increases.

This means we can check its voltage output signal behavior by tapping into the light blue with red stripe (LT BLU/RED) wire of the MAF sensor's 6-wire connector (with a multimeter) and revving the engine up and down.

If the sensor is working correctly, its voltage output signal should increase when we rev the engine up. When we let go of the throttle and engine RPMs drop, the MAF signal voltage output should drop too.

Usually, when the MAF sensor has kicked the bucket, its voltage signal will stay stuck at one value no matter how much we rev the engine up or down.

IMPORTANT: Your Ford Escape's MAF sensor must remain plugged into its connector while checking its MAF signal voltage output. You'll need to back-probe the connector or pierce the wire with a wire-piercing probe. If you don't either of these tools, this is the one I use and recommend: Goupchn 4mm Banana to Banana Plug Test Leads Kit (Amazon affiliate link).

OK, let's get this show on the road:

1. 1

   Set your multimeter to Volts DC.

2. 2

   Attach the black multimeter lead to the battery's negative (-) post.

3. 3

   Hook the red multimeter lead to the light blue with red stripe (LT BLU/RED) wire using the right probing tool.
   
   This LT BLU/RED wire connects to terminal number 5 on the MAF sensor connector (see diagram above).

4. 4

   Start the engine and let it idle.
   
   Once the idle evens out, take note of the voltage reading on your meter. It may bounce around a little —and that's normal. This initial number is your base MAF signal voltage.

5. 5

   Accelerate the engine by opening the throttle.
   
   You can do this by moving the throttle linkage at the throttle body or by having a helper step on the gas pedal.

6. 6

   The MAF signal voltage should climb as RPM goes up.

7. 7

   Release the throttle to bring the engine RPM back down.

8. 8

   The voltage should drop as the RPMs come down.

9. 9

   Repeat the rev-up/release test several times to confirm the results are consistent.

Let's see what your result means:

CASE 1: The MAF signal voltage went up as you raised engine RPM and dropped back down when you let off the throttle. This is what it should do and it tells you the MAF sensor is functioning correctly.

If you've got a P0102 (MAF Signal Low) or a P0103 (MAF Signal High) stored, whatever triggered the code isn't showing up right now —since the signal is responding to RPM changes instead of being stuck too high or too low.

CASE 2: The signal voltage stayed the same no matter how much the engine speed changed. This usually means your Ford Escape's MAF sensor has failed.

Before calling the sensor bad, we need to do a few more checks. Go to: TEST 2: Making Sure The MAF Sensor Is Getting Power (VPWR).

TEST 2: Making Sure The MAF Sensor Is Getting Power (VPWR)

Your 3.0L V6 Ford Escape or Mazda Tribute MAF sensor's two hot wires need 12 Volts (VPWR) to do their thing.

This VPWR voltage is delivered by the white with red stripe (WHT/RED) wire that connects to female terminal 2 of the sensor's 6-wire connector.

Since in TEST 1 you got a voltage signal that was stuck at one value, we're going to make sure these hot wires are getting power by doing a simple multimeter voltage test at terminal 2 of the MAF sensor connector.

This voltage is only present when the key is in the RUN or START position. For our testing purposes, we'll check the availability of this power with the key in RUN but the engine OFF.

IMPORTANT: Take care when probing the front of the female terminal of the connector with your multimeter test lead, since it can easily get damaged. If it does, you'll need to replace the connector.

These are the test steps:

1. 1

   Unplug the MAF sensor from its connector.

2. 2

   Set your multimeter to Volts DC.

3. 3

   Attach the black multimeter lead to the battery's negative (-) post.

4. 4

   Lightly probe the female terminal number 2 with the red multimeter lead.
   
   Terminal 2 should correspond to the WHT/RED wire of the MAF sensor's 6-wire connector.

5. 5

   Switch the key to RUN, but don't crank or start the engine.

6. 6

   The multimeter should show 10 to 12 Volts.

Let's see what your test result is telling us:

CASE 1: Your multimeter showed 10 to 12 Volts. So far so good, since it confirms the MAF sensor is getting its VPWR voltage supply.

The next thing to check is that the MAF sensor also has chassis Ground (PWR GND). Head over to: TEST 3: Making Sure The MAF Sensor Is Getting Ground (PWR GND).

CASE 2: Your multimeter did not show 10 to 12 Volts. Double-check your multimeter connections and run the test again.

If you still don't get a 10 to 12 Volt reading, then you know the problem isn't the MAF sensor itself —because without that VPWR voltage, it can't work at all.

Your next step is to find out why the voltage is missing on the RED wire and repair it, so your Escape's MAF sensor can do its job and the DTC can clear.

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

The MAF sensor hot wires, besides needing 12 Volts to function, also need a connection to chassis Ground.

This chassis Ground (PWR GND) is provided by the black (BLK) wire that connects to terminal 3 of your MAF sensor's 6-wire connector.

Since this PWR GND is a chassis Ground, it's available at all times. In other words, no matter what position the key is in (OFF, RUN, or START), this Ground is available to the MAF sensor.

To make sure this circuit is delivering chassis Ground, we're going to do a simple multimeter voltage test.

IMPORTANT: Be careful not to damage the front of the connector or female terminal with the multimeter test lead, or you'll need to replace the connector.

These are the test steps:

1. 1

   Disconnect the MAF sensor from its electrical connector.

2. 2

   Place your multimeter in Volts DC mode.

3. 3

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

4. 4

   Gently probe female terminal number 3 with the black multimeter test lead.
   
   Terminal number 3 should connect to the BLK wire of the MAF sensor connector.

5. 5

   You should see 10 to 12 Volts on the multimeter.
   
   NOTE: Since this is a chassis Ground, it's available at all times whether the key is ON or OFF.

Now let's break down what your results mean:

CASE 1: The multimeter showed 10 to 12 Volts. That's the correct reading and it tells you the MAF sensor does have chassis Ground.

The next step —and the last one— is to make sure your Ford Escape's PCM is providing the sensor Ground (MAF RTN) to the MAF sensor. Go to: TEST 4: Making Sure The MAF Sensor Is Getting Ground (MAF RTN).

CASE 2: The multimeter DID NOT show 10 to 12 Volts. That means the MAF sensor isn't getting chassis Ground.

Check your test connections and try again. If the reading is still not there, you can rule out the MAF sensor itself —because without the BLK wire providing chassis Ground, it can't work.

Although it's the beyond the scope of this tutorial, your next step is to find out why chassis Ground is missing and fix the issue.

TEST 4: Making Sure The MAF Sensor Is Getting Ground (MAF RTN)

If you've reached this test section, you have confirmed that:

• The MAF signal voltage output is stuck at one value, regardless of engine RPM (TEST 1).
• The sensor is receiving VPWR power (TEST 2).
• It's also getting its PWR GND (TEST 3).

For your final test, you're going to make sure the sensor is receiving its MAF RTN Ground at terminal 4, which is provided directly by the PCM.

Checking the presence of this MAF RTN Ground at terminal 4 follows the same procedure as the previous tests we've done so far: a simple multimeter voltage test to check for its presence.

CAUTION: This Ground is provided internally by your Ford Escape's PCM. Be careful not to connect this wire to battery 12 Volts, or you'll deep-fry the PCM. The multimeter voltage test I'm suggesting in the instructions below is a safe way to check for the presence of MAF RTN Ground in this circuit.

These are the test steps:

1. 1

   Disconnect the MAF sensor from its electrical connector.

2. 2

   Place your multimeter in Volts DC mode.

3. 3

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

4. 4

   Gently probe female terminal number 4 with the black multimeter test lead.
   
   Terminal number 4 should correspond to the TAN/LT BLU wire of the MAF sensor connector.

5. 5

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

6. 6

   You should see 10 to 12 Volts on the multimeter.

OK, let's interpret your test result:

CASE 1: The multimeter showed 10 to 12 Volts. This tells you the MAF RTN circuit is OK and the sensor is getting its sensor Ground from the PCM.

If the following checks are true, then you can conclude the MAF sensor is bad and needs to be replaced:

• In TEST 1, the MAF signal stayed stuck at one value no matter the engine speed.
• In TEST 2, the sensor was confirmed to be getting 10 to 12 Volts (VPWR).
• In TEST 3, the sensor was confirmed to be receiving chassis Ground (PWR GND).
• And in this section, the MAF RTN circuit was confirmed to be providing Ground from the PCM.

When it's time to swap it out, I want to recommend these two MAF sensors from two automotive brands I have used many times over the years and don't hesitate to recommend:

• Walker Products 245-3102 Mass Air Flow Sensor Assembly (Amazon affiliate link).
• Delphi AF10128 Air Flow Sensor (Amazon affiliate link).

CASE 2: The multimeter DID NOT show 10 to 12 Volts. This means the PCM is not providing a sensor Ground (MAF RTN) to the MAF sensor.

Go back and double-check your multimeter connections and rerun the test. If the reading still doesn't show 10 to 12 Volts, you can rule out the MAF sensor itself —it can't work without the MAF RTN Ground supplied by the PCM.

Although beyond the scope of this tutorial, your next step is to find out why the Ground is missing and repair it.

More 3.0L V6 Ford Escape Diagnostic Tutorials

You can find a complete list of 3.0L V6 Ford Escape, Mercury Mariner and Mazda Tribute diagnostic tutorials in this index:

• 3.0L V6 Ford Escape Index Of Articles.

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

• How To Test The Fuel Injectors (2001-2004 3.0L Ford Escape).
• How To Test Engine Compression (2001-2012 3.0L V6 Ford Escape, Mercury Mariner).
• How To Test For A Blown Head Gasket (2001-2012 3.0L V6 Ford Escape, Mercury Mariner).
• How To Test The Fuel Pump (2001-2004 3.0L Ford Escape).