How To Test The MAF Sensor (2001-2004 2.0L Ford Escape)

The mass airflow (MAF) sensor on your 2001-2004 2.0L Ford Escape (Mazda Tribute) can be tested with a multimeter.

What makes it easy to test is, first, the fact that it's very accessible —it's right there in the open— and second, its signal output can be checked with a multimeter (no scan tool needed).

In this tutorial, I'm going to show you the four tests you need to do to determine if it has failed or if it's OK and the issue lies elsewhere.

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

By the end of your tests, you'll know if the MAF sensor is toast and needs replacement.

APPLIES TO: This tutorial applies to the following vehicles:

• 2.0L Ford Escape: 2001, 2002, 2003, 2004.
• 2.0L Mazda Tribute: 2001, 2002, 2003, 2004.

Symptoms Of A Bad MAF Sensor

The mass air flow (MAF) sensor measures the amount of air entering the engine. Your Escape or Tribute's powertrain control module (PCM) then uses that information to calculate how much fuel to inject into the cylinders.

If the MAF sensor starts sending incorrect readings —or fails completely— the computer can't manage the air/fuel mixture the way it should. The result is poor engine performance, often with one or more of these symptoms:

• 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: The 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

To properly test the MAF sensor, you need to know the role of each of the six wires in its connector.

The table below gives a brief description of what each wire does:

Terminal	Wire	Description
1	Orange (ORG)	IAT Sensor Signal
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	Pink with black stripe (PNK/BLK)	SIG RTN -IAT sensor Ground

Where To Buy The MAF Sensor And Save

The following MAF sensors are of known automotive brands (brands that I use myself):

NOTE: Not sure if the indicated MAF sensors fit your particular Ford Escape? Don't worry. Once you get to the site, they'll ask you for the specifics of your particular vehicle. If it doesn't fit, they'll find you the right one.

TEST 1: Testing The MAF Signal

Our first diagnostic step is to check the MAF sensor's signal and see if it changes with engine airflow —which is directly tied to engine RPM.

More specifically, here's what we're confirming:

• If the MAF sensor is good, its voltage signal rises as RPM increases and drops as RPM decreases.
• If the MAF sensor is bad, its voltage usually stays stuck at one value no matter how much engine speed changes.

To see if these signal voltage changes actually occur, we're going to tap into the white with blue stripe (LT BLU/RED) wire of the MAF sensor's connector using either a back probe or a wire-piercing probe.

IMPORTANT: The MAF sensor must stay plugged into its connector during this test. You'll need to back-probe the connector or pierce the wire with a wire-piercing probe. If you don't have either of these tools, this is the same tool I use and recommend: Goupchn 4mm Banana to Banana Plug Test Leads Kit (Amazon affiliate link).

Alright, let's get going:

1. 1

   Set your multimeter to Volts DC.

2. 2

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

3. 3

   Connect the red multimeter test 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).
   
   NOTE: The MAF sensor must stay plugged into its 6-wire connector during this test.

4. 4

   Start the engine and let it idle.
   
   Once the idle evens out, take note of the voltage reading on your multimeter. 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 interpret your MAF signal test results:

CASE 1: The signal voltage rose when you revved the engine and dropped when you let off the throttle. This is the normal response and confirms the MAF sensor is working properly.

If a P0102 (MAF Signal Low) or P0103 (MAF Signal High) is registered in the PCM's memory, whatever triggered them isn't happening right now —because the MAF signal is moving with RPM changes instead of staying stuck high or low.

CASE 2: The signal voltage stayed locked on one value no matter how engine speed changed. This usually indicates the MAF sensor is toast.

To make sure the sensor has kicked the bucket, there are still a couple of checks left. Next up is to make sure its getting power: TEST 2: Making Sure The MAF Sensor Is Getting Power (VPWR).

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

For the MAF sensor's hot wires to work —and for the sensor to send an usable signal to the PCM— it needs a 12-volt power supply (VPWR).

In this step, we'll verify that female terminal 2 is delivering between 10 and 12 Volts to the sensor.

This VPWR feed comes into terminal 2 through the white with red stripe (WHT/RED) wire of the MAF sensor's 6-wire connector.

One last thing: the VPWR supply is only available with the key in the RUN or START position. We'll confirm its presence at terminal 2 (with our multimeter) with the key in RUN but the engine OFF.

IMPORTANT: Be careful when probing the front of the connector. Don't force the multimeter test lead in —if you damage the female terminal, you'll be stuck replacing the entire 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 test lead to the battery's negative (-) post.

4. 4

   Lightly probe the female terminal 2 with the red multimeter test lead.
   
   Terminal 2 should correspond to the white with red stripe (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 interpret your test result:

CASE 1: The multimeter reads 10-12 Volts. That's the correct result and confirms the MAF sensor is getting VPWR voltage.

Next, we need to make sure the MAF has a solid chassis Ground (PWR RTN) connection, head over to: TEST 3: Making Sure The MAF Sensor Is Getting Ground (PWR GND).

CASE 2: The multimeter does not read 10-12 Volts. Double-check your multimeter test lead connections and repeat the test.

If VPWR voltage is still missing at terminal 2, the MAF sensor itself isn't the issue —its hot-wires can't work without a proper 12-Volt feed.

Your next step is to find out why the WHT/RED wire isn't delivering VPWR power and fix it so the MAF can operate and you can clear the DTC.

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

So far, your tests have confirmed:

• The MAF sensor's signal voltage stays stuck at one value regardless of engine speed (TEST 1).
• The MAF sensor is getting 10–12 Volts (VPWR) from female terminal 2 (TEST 2).

Now we'll check that the black with orange stripe (BLK) wire at female terminal 3 is supplying chassis Ground (PWR GND) to the MAF sensor.

Since this PWR GND is a chassis Ground, it should always be present at terminal 3 —whether the key is ON or OFF.

IMPORTANT: Be careful not to damage the connector or female terminal with your multimeter test lead —otherwise you'll end up replacing the entire 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 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.

Here's how to interpret your results:

CASE 1: The multimeter showed 10-12 Volts. That's the correct result and it confirms the MAF sensor is getting chassis Ground (PWR GND).

Four our final diagnostic test, we need to make sure your Ford Escape or Mazda Tribute's PCM is supplying 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 10-12 Volts. This means the MAF sensor isn't receiving chassis Ground.

First, recheck your multimeter connections and repeat the test. If the reading is still missing, you can rule out the MAF sensor itself —since it can't operate without the BLK wire supplying PWR GND Ground.

Your next step is to track down why this chassis Ground is missing and repair it. This should get the MAF sensor working again.

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

For our final MAF sensor test, we'll verify that the MAF sensor is receiving the MAF RTN Ground from the PCM.

The MAF RTN Ground is carried on the tan with light blue stripe (TAN/LT BLU) wire, which connects to female terminal 4 of the MAF sensor's 6-wire connector.

IMPORTANT: Take care not to damage the front of the connector or the female terminal with your multimeter test lead, or you'll end up replacing the connector.

CAUTION: This Ground is generated inside the fuel injection computer. Never apply battery voltage to this wire, or you'll destroy the PCM. The multimeter voltage test described below is a safe way to confirm the presence of 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 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.

Let's see what your test results mean:

CASE 1: The multimeter read 10-12 Volts. That's the correct result and it confirms the PCM is providing sensor Ground (MAF RTN) to the MAF sensor.

At this point, you can call the MAF sensor bad and replace it, if you've confirmed:

• The MAF signal stays stuck at one value regardless of engine speed (TEST 1).
• The MAF sensor is getting VPWR (TEST 2).
• The MAF sensor has chassis Ground (TEST 3).
• The PCM is supplying MAF RTN sensor Ground (this test section).

If all four checks line up, the MAF is toast. When you're ready to replace it, here are two known automotive brands I've used over the years and can recommend without hesitation:

• 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 read 10–12 Volts. This means the MAF sensor isn't receiving sensor Ground (MAF RTN) from your Ford Escape or Mazda Tribute's PCM.

Recheck your multimeter leads and repeat the test. If the reading is still missing, you can rule out the MAF sensor itself as the cause of the MAF signal failure in TEST 1 —it can't generate a signal without the PCM's MAF RTN Ground.

Your next step is to figure out why this MAF RTN Ground is missing and restore it. The most likely cause is an open-circuit problem in the TAN/LT BLU wire somewhere between the MAF connector and the PCM.

More 2.0L Ford Escape Diagnostic Tutorials

You can find a complete list of diagnostic tutorials for the 2.0L Ford Escape (Mazda Tribute) in this index:

• 2.0L Ford Escape Index Of Articles.

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

• How To Test The Starter Motor (2001-2004 2.0L Ford Escape).
• Oxygen Sensor Heater Test -P0135 (2001-2004 2.0L Ford Escape).
• How To Test The Fuel Injectors (2001-2004 2.0L Ford Escape).
• How To Test For A Blown Head Gasket (2001-2004 2.0L Ford Escape).